Operation and Calibration of
the
Modularized Spectrum Analyzer,
Original or SLIM MSA/TG/VNA
Page Started Feb. 26,
2004
Updated April 4, 2009,
Re-design this page to reflect new MSA software, Version 113.
Updated Aug 1, 2009,
Re-design this page to reflect new MSA software, Version 114.
Special Notice for XP
users,
Read the following for possible XP
Problems (at end of this page)
Updated Aug 26, 2009,
Change PDM Calibration Procedure (I goofed up in the original version)
Updated Sept 1, 2009,
Correct sign error at E.4.a. was -10.75
- 20 = 30.75, should be -30.75
The MSA can be
constructed and operated as a multi-functional device. At this
time these functions are: a Basic Spectrum Analyzer, a
Spectrum Analyzer with Tracking Generator, and a Vector Network
Analyzer. The computer software is written to support all these
functions with either the Original or SLIM MSA.
This page will
describe the Operation of the MSA as a Basic Spectrum Analyzer or
Spectrum Analyzer with Tracking Generator. Separate pages
describe the Operation of the MSA as a VNA. The descriptions
include the
necessary steps
to make the MSA fully functional, with Initial Set-Up and
Calibration procedures.
Use
your
browser's "Refresh"
button for the latest updates. If you came to this
page from a Link,
return by using your
browser's Back button. As a "first time" MSA user, I suggest you
first become
familiar with the section: "Operational Descriptions of the MSA".
I.
Operational Descriptions
of the MSA
A.
Spectrum Analyzer Mode (SA
Mode) (this page)
Controls for the
Spectrum Analyzer
Special Testing
in
the Spectrum
Analyzer Mode
Using the Features
of
the Spectrum
Analyzer
B.
Vector
Network Analyzer Operation (separate page)
1. VNA,
Transmission Mode
Controls for
the VNA, Transmission Mode
Special
Testing
in
the VNA, Transmission Mode
Using the
Features of
the VNA, in the Transmission Mode
2. VNA, Reflection
Mode (new page under construction)
II. Initial Set-Up for MSA
Before
the MSA is operational, these procedures must be followed:
A.
MSA Software Download and Installation
B. Hardware Configuration
MSA Hardware
Computer Hardware Configuration
C. Software Configuration
Configuration Manager Window
Calibration File Manager Window
III.
Calibration Procedures for the
MSA
For the MSA to
be accurate, calibrations must be performed, in this
order:
A.
Coaxial
Cavity Filter, Tuning
Procedure
B.
Master Oscillator Calibration
C.
Resolution
Bandpass Filter Calibration
D. Phase
Detector Module Calibration (VNA only)
E. Path
Calibration for Magnitude (and Phase for VNA)
F. Frequency Calibration for
Magnitude
F1.
Manual
Frequency Calibration for
the Basic MSA, or
F2.
Semi-Automatic
Frequency
Calibration for the
MSA/TG
I.
Operational Descriptions of the MSA
At the present time, the software
is written for a fully
configured MSA to operate as a Spectrum Analyzer, or as a Vector
Network Analyzer (VNA). The Spectrum Analyzer will measure signal
Magnitude versus Frequency in scales of dBm, Watts, or Volts. The
VNA will measure signal Magnitude and Phase, versus Frequency. Later, more will be
written for using the
MSA as a Scalar Network Analyzer, and VNA operation with a Reflection
Bridge.
Operational descriptions are given
with the assumption that
the MSA
is fully configured for the Tracking Generator and VNA topology.
And, that it is functional, and calibrated. A Basic MSA will not have
some of the features or functions that will be described.
Be aware that the MSA software
program,
like
any other program, can create conflicts inside your computer while
other
programs are running. "Other programs" include, moving your
Mouse,
having a Mouse connected to the computer via USB, wireless
devices, an Internet Browser, just to name a few.
Graph Window for MSA
The MSA Graph
Window is the visual output of the MSA and has three main sections, the Menu
Items, the Graph Display and the Control Panel. The Menu Items
are for general interface and selecting Modes of operation. The
Graph Display
contains the traces and their supporting information. The Control
Panel contains the Buttons, Boxes, and hidden windows to control the
MSA for each specific Mode of operation. I expect
the MSA Graph Window to change often, as the MSA project continues.
The Graph Window has been formatted for 800 pixels
by 600 pixels. However, it can be "re-sized" by "mouse grabbing"
a corner (or side) to expand or contract. Read about possible
XP
Problems at end of this page.
A. Spectrum
Analyzer
Mode (SA Mode)
Open and Run the MSA
Program "spectrumanalyzer". The following is a screen print of
the Graph Window while sweeping in the
Spectrum Analyzer Mode. No signal is input to the MSA. The
Center Frequency is 0 Hz. This
is the initial default, "self-test", for the MSA. 
The
lower right Button, labeled "Restart", indicates that the MSA is
Halted. While actively sweeping, it is labeled "Running. To Halt
the sweep, position the Mouse cursor over
any of
the three Buttons, "Halt", "Halt At End", or "Running", and "Left
Click" the Mouse. The sweep
will stop and the MSA will enter the
"Halted" mode.
While Halted, there is no
obvious activity on the display. But,
the software is continually running in the background. It
is waiting for the user to exercise an option.
The operator
will normally change the operating parameters when the sweep is
Halted, but some can be changed while actively
sweeping. If the program ever hangs up and won't respond, use the
standard "Ctrl/Alt/Del" for Windoze, and close the program.
To normally exit the MSA program, Halt the sweep, then, put the
mouse pointer over the X button in the upper right corner of the Graph
Window, and left click. The Graph
Window will close (disappear). The program will completely close.
Controls for the Spectrum Analyzer
Indicators
A small arrow below the graph's baseline indicates
where the sweep has halted. It also indicates the direction of
the sweep.
A "Marker" Table in the lower
left,
under the Graph, displays the
Frequency and Magnitude measurements of any markers that have been
selected.
A table in the upper right displays the present
configurations.
Boxes and Buttons
"Continue" button. This will allow the Spectrum Analyzer
to continue sweeping from the point at which it was halted. In
some cases, the button will not be accessable, only a "Restart" is
allowed. During sweeping this button will change its name to "Halt". When it is clicked,
the sweep will halt immediately.
"Restart" button.
This will cause the Spectrum Analyzer to restart the sweep on the first
step. A short period of time will occur before sweeping actually
begins. During this time the MSA is going through a
re-initialization and is calculating all of the points for the next
sweep. During sweeping this button will
change its name to "Runnning".
When it is clicked, the sweep will halt immediately.
Note: Pushing the keyboard's
"Alt" key will interrupt the sweep and the MSA program. Pushing the "Alt" key again
will return to sweeping.
"One
Step"
button. This will advance the Spectrum Analyzer measurement from
the last point where it was Halted,
by one step. Each click on this button will step the
frequency once and automatically Halt. During normal sweeping this button
will change its name to "Halt At End".
When it is clicked, the sweep will halt at the end of the sweep.
"Redraw" button. It is
possible that the graph may suffer a loss of information if it is
obscured by another window. If so, the Graph and its data can be
"Redrawn" with this button.
"Marker" pull-down box.
This will select a labeled marker to be installed into the Graph.
The procedure is to select a marker in this box, then move the mouse
pointer over the trace where you want the marker. Double click
the left mouse button. If
"None" had been selected, the "L" marker will be installed into the
Graph and "L" will be inserted into the "Marker" selection box. A
marker will be placed on the data point, closest to the mouse
pointer. The values of the data point will be displayed in the
Marker Table.
"Delete" button.
This will delete the selected marker from both the Graph and the Marker
Table.
"Clear Marks"
button. This will delete all of the markers from both the Graph and the Marker
Table. The Marker Table will disappear, but will return after the
next "Restart" and "Halt".
"MHz" box.
This will display the frequency at which the selected marker is
positioned on the Graph. You may insert any frequency, within
the range of the span, into the "MHz" box, and click the "Enter"
box. The selected marker will move to that position on the
Graph. If the inserted frequency is between two valid data
points, the marker position and its displayed data will be an
interpolation between the two valid points. Clicking the "+" or "-" buttons will move
the selected marker to the next closest valid data point, one step at a
time.
"Mark->Cent"
button. This will change the Center Frequency to be the
frequency of the selected marker. It will take effect upon
clicking the "Restart" button.
"Expand L-R" button. This
will change
the span of the Sweep to be between the "L" and "R" markers. It
will
take
effect upon clicking the "Restart"
button. The "L" marker can be on the right side of the "R" marker.
"STO Config" and "RCL
Config"
buttons.
This will access up to 21 memory locations for storing or recalling the
Configurations, for this session only. They will be empty at the
start of each new session.
Store a configuration by
typing 0 to 20 in the box. Click
the "STO Config" button. The present configuration settings will
be stored in that memory location.
You
can recall a stored configuration by typing
its memory
location into the
box and then click the "RCL Config"
button. This will configure the MSA with the
configuration settings that were stored in that memory location.
It will take effect when "Restart" is clicked.
Message
box. This is an area under the left side Graph that is
normally invisible. This box displays any messages that are
created within
the program. If an error message is displayed, the system will
automatically halt. The program must be exited and the error
corrected before running again.
"Date:Time" text. This is an area above
the center of the Graph.
It displays the date and time. You can double click this area to
open a "Title" window and insert any three lines of text you
desire. This is useful for displaying information you would like
to be printed with the Graph. You can over-write the date;time
stamp, but it will return on the next "Restart".
Windows within the Graph
Window, normally hidden.
The
Sweep Parameters Window
While Halted, position the mouse
cursor in the area just below the Graph's baseline and double left
click. The Sweep Parameters Window
will open. It contains the buttons and boxes used to control
the
parameters of the Spectrum Analyzer. You may also double click in
the text area of the displayed parameters in the upper right to open
the Sweep
Parameters Window.
"Data Mode"
drop-down box. This selection determines what data will be
Graphed.
* 0(Normal Operation) is the default for Graphing normal mode
measurements.
* 1(Graph Mag Cal) will plot the Calibration Table for the selected Path
*
2(Graph Freq Cal) will plot the Frequency Calibration Table (sweep from 0 to 1000 MHz)
*
3(Graph Noisy Sine) will plot a fictional set of sine wave points (sweep from 0 to 1000 MHz)
*
4(Graph 1MHz Peak) will plot a fictional set of data
points at 1 MHz
*
5(RLC) will plot a fictional set of data
points, representing a series 25 ohms and .001 ufd placed between the
TG and MSA
input. This will give a meaningful graph in the range of 100 KHz
to 10 MHz. This data is useful to illustrate the graphing of an
equivalent RC circuit. Much more will be written on these
"fictional"
measurements.
"Select Final Filter Path:"
drop-down box. A selection here will tell the program which
Final Xtal
Filter Path is used.
It
will send signals to an optional Bank of Switched Filters.
These filters determine the
Resolution Bandwidth of the MSA. Path 1 is the Default
path. When selecting a different
filter path, the "Restart" must be
clicked for the system to be accurate. The software will use a
specific table of path correction values for each Path, to compensate
for MSA inaccuracies. "P1" denotes Path 1, the "10.694785"
denotes the Final I.F. frequency, and the "4" denotes the filter path
has a 4 KHz bandwidth.
"Video Filter BW"
drop-down box. You must "tell" the sofware the position
of the Video Bandwidth Selector Switch . At this time, no
commands are
given, but this will be expanded in a future version of software.
"Graph Appearance". This
is a choice of background color for the Graph Window.
"Refresh Screen Each Scan" check box.
Click box to check or uncheck. When checked, the Graph will
refresh itself on the end of each sweep. If the box is unchecked,
the Graph will not be refreshed until the sweep is Halted. This
is a user preference.
"Display Sweep Time" check box.
Click
box to check or uncheck. When checked, the sweep time, in
seconds, is
displayed between the Message Box, but only during active sweeping.
"Spur Test" check box. Click box to check or
uncheck. When checked, it is a method to verify if a
signal on
the Graph is a real input signal or a spur that is created by the
Spectrum Analyzer. The Spur Test will activate
when clicking
the "OK" and "Restart" buttons. This test will change the
Phase
Detector Frequency of PLL 1, a small amount. If a questionable
signal on the
graph changes location or goes away when the sweep is resumed, it means
the signal is a spur that is self-generated within the MSA. It is
not a real signal entering the input of the MSA. To return to
Normal operation, remove the check from the "Spur Test" check
box. Then click "OK" and "Restart".
"Signal Generator" or
"Tracking Generator" button. This
controls the mode of the tracking generator. Clicking the button
will select
either the Signal Generator Mode or the Tracking Generator Mode.
The program will update with entered values when the "Restart"
is
clicked.
When the Button is labeled "Signal Generator", the Tracking
Generator output
is used as a CW Signal Generator. It will be
a fixed frequency corresponding to the value that is entered in the
"Enter Freq" Box. The default frequency will be displayed
the "Enter
Freq" Box. The operator may enter any frequency
(in MHz) between -90 and 1200, with 6 places of decimal accuracy.
Negative values are acceptable. The Tracking Generator output will be
a positive frequency, but a negative value will
command the PLO3 to a lower frequency, for special testing. The
limits are determined by the range of PLO3.
When
the Button is labeled "Tracking
Generator" and the right button is named "Normal", the Tracking Generator output
will be the same frequency as what the Spectrum Analyzer is tuned to,
plus a value of frequency offset entered in the "Enter
Offset" box. If the Offset is "0", which
is the default,
the output frequency will be the same as what the MSA is commanded
to. The output will "Track" the MSA, step for step, throughout
its entire frequency range.
If an offset is entered, for example
"-.455", the output will always be 455 KHz below the MSA commanded
frequency. The offset value is limited in two ways. One, by the range of PLO3, and two, at
what frequency the MSA is commanded to. The offset value should
not allow the Tracking Generator to output a frequency below 0 MHz nor
above the maximum limit of the MSA, which is nominally, 1050 MHz.
When
the Button is labeled "Tracking
Generator" and the right button is named "Reverse", the Tracking Generator will
"reverse track" the
MSA commanded input frequency. The MSA will sweep from a
lower frequency to a higher frequency. But, the Tracking
Generator output will sweep from a higher frequency to a lower
frequency. The two frequencies will intersect in the center of
the sweep with an offset determined by the value entered into the "Enter Offset" Box. For
example, if the MSA is commanded to sweep from 1 MHz to 2 MHz and
the Offset is "0", the Tracking Generator will sweep from 2 MHz to 1
MHz. Both the MSA and the Tracking Generator will be 1.5
MHz at the center of the sweep. If the offset is -.455 MHz, the
Tracking Generator will sweep
from 1.545 MHz to .545 MHz and be 1.045 MHz at the center. This is quite useful when
testing
radios with a "reversed" I.F.
Note: When in
either the Signal Generator Mode, or Tracking Generator Mode,
there will always be a frequency exiting the Tracking Generator
port. There is no provision to disable it. The Tracking
Generator output is not confined to a fundamental frequency.
There
will be
other frequencies generated by PLO3 within the MSA/TG. Sometimes
this can affect normal MSA operation. When in the Spectrum
Analyzer Mode, it is advisable to "park" the Signal Generator to a
frequency that will not affect spectrum analyzer operations. I
suggest "parking" the Signal Generator to a frequency above the
selected sweep of the Spectrum Analyzer. It is possible to
attribute strange spurious to the Signal Generator. If so, move
the frequency of the Sig Gen and see if the spurious move or disappear.
"Cent" box. This is the box to
enter the Center Frequency of the sweep. Enter the frequency in
MHz. 25.0 MHz can be
entered as "25"; the decimal and zero's are not necessary. 25.200
MHz would
be entered as "25.2" ; 455 KHz, ".455" ; 1 Hz,
".000001". And, yes, "0" is a valid center frequency.
"Span" box. This is the box to enter the Sweep Width. Enter the
range in MHz, with the same consideration for
decimals and zeros as in the "Cent" box. Here again, "0" is
a valid sweep width. Use "0" when you want the MSA to "zero
sweep" at
a
fixed center frequency, while displaying the signal's activity.
The terms "span" and "sweep width" have the same meaning.
"Start" box. When the
Start Stop box is checked, the "Start" box will accept a value that
represents a start frequency.
"Stop" box. When the Start Stop box is
checked, the "Stop" box will accept a value that represents a stop
frequency.
"Steps/Sweep" box.
Enter the number of steps to compose a
single sweep. Valid numbers are from 1 to 40000. Keep an
even number if you want the commanded center frequency to be at
the
center of the Graph. I suggest using a number that is a
submultiple of the Sweep Width. This will assure a "whole"
number being displayed for each
sweep step. I like 400
steps, as this will prevent an 800 pixel computer monitor from
"self-interpolating". Sweeping begins at step number 0 and ends
on the step
number entered into the "Steps/Sweep" box. There will always be
one more data point than the value of "steps", because, data point
number "0"
is included. Example: entering the value of "2" will result in
three data points and two full steps, stepping from point number 0 to
point number
1, then point number 1 to point number 2. Point numbers and step
numbers are treated as the same value (step 135 = data point 135).
"Wait
(ms)" box. As this
value
is increased, the sweep
is slowed and the measured data becomes more precise. As a
general
rule of thumb, if the Video Bandwidth Selection Switch is selecting
Wide bandwidth (center position), then enter 0 or 1, for fastest
response with minor data error. For Medium video bandwidth ,
enter 1 to 10. For Narrow bandwidth, enter 10 to 500.
Higher values are fine. The amount of real time for
each
whole
number increment is approximately 1 millisecond. Valid numbers are 0
and any whole number above 0. You may resume sweeping without
having to use "Restart".
"Number of Divisions" drop-down box. This selects
the number of vertical reference grid lines along the horizontal
axis. Default is "10".
"Sweep" options
table. The following check boxes determine the sweep
preferences.
* "Linear".
This is
the default and normal sweep.
* "Log".
This
performs a log sweep. When checking, the "Start" and "Stop" boxes
become active. Valid inputs are frequencies greater than 0
(MHz). Negative frequencies and very narrow spans will not be
allowed.
* "L-R". This performs sweeping
from Left to Right, low frequency to higher frequency.
* "R-L". This performs sweeping
from Right to Left, high frequency to lower frequency.
* "Alternate". This performs
sweeping from Left to Right, then Right to Left.
"OK" button.
Clicking will close the window and cause the program to use any changes
made within the window.
"Cancel" button. Clicking
will close the window and any changes made within the window will be
disregarded by the program.
The Magnitude Axis Window
While Halted, position the mouse
cursor over any of the Magnitude Scale values and double left click.
The "Axis Y2" Window
will open. It contains the buttons and boxes used to control the
parameters of the magnitude trace.
"Trace Color" box. Click within the box to
open a Color Window. You may choose a variety of colors for the
trace.
"Trace Width" pull-down box. You may
select 3 different trace widths. The numbers correspond to the
number of pixels used to create the trace. The default value "1"
is the best performer, and 2 or 3 are more suitable for histograms.
"Trace Style" pull-down box. This box has 5 selections
for desired trace.
* "Off"
The trace will not be displayed the Graph Window. However, the
data will be collected and the Marker Table will update.
* "Norm
Erase" The data point is
connected to the previous data point by a line. Each trace will remain on the graph until the
next sweep, where it will be erased and re-written at each step.
This is the
most common display for spectrum analyzers. I should caution that
connecting data points with a line will give the visual impression that
the data is valid between data points. This is not the case for
the MSA or any analyzer using a "stepped" response.
* "Norm
Stick" Same as
Norm Erase, except the traces will not be erased. They will be overwritten by
subsequent sweeps. This is useful for accumulated peak readings.
* "Histo
Erase" The data point is represented by a
Histogram. This is a
vertical line from the base of the graph to the magnitude level of the
signal. Each histogram will remain on the graph until the next
sweep, where it will be erased and re-written with new data.
* "Histo
Stick" Same as Histo Erase, except the
histograms will not be erased.
They will be overwritten by subsequent sweeps. This is useful for
accumulated peak readings.
"Number of Divisions" pull-down box.
You may select the number of horizontal graph reference lines, from 4
to 12.
"Graph Data"
pull-down box. This will define the Scale and Trace to
display the data in one of three measurement options:
* "Magnitude (dBm).
This is the default and most common measurement scale for a Spectrum
Analyzer. The
Magnitude is measured and scaled in dBm. (decibels, referenced to 1
milliwatt)
*
"Magnitude (Watts). The
Magnitude is measured in dBm and then converted
and scaled to Watts.
*
"Magnitude (Volts). The
Magnitude is measured in dBm and then converted
and scaled to Volts.
"Top
Ref"
box. and
"Bot
Ref"
box. Numbers entered into
these boxes will assign the Reference values for
the vertical Magnitude scale on the Graph.
When displaying Magnitude in the dBm scale, the value of the
"Top Ref" box usually, will not be greater than the maximum input range
of the MSA, in
dBm, but it is permissible. The "Bot Ref" value is usually chosen
to be below the noise
floor of the MSA. The operator can make the
difference between the Top and Bottom reference values as little as .1
dB. For general measurements, I like a difference value of 100
dB. Example: -20 for the top and -120 for the bottom.
When displaying Magnitude in the Watts or Volts
scale, do not enter a value less than 0 into the "Bot Ref" box..
"Auto Scale"
check box. A check will allow the program to
create a scale that is appropriate for the level that is
measured. Apply a check mark here when changing an option in the
"Graph Data" pull-down box. This will assure a trace on the
graph. Uncheck this when manually entering values into the "Top
Ref" or "Bot Ref" box.
"OK" button. Clicking
will close the window and cause the program to use any changes made
within the window.
"Cancel" button. Clicking
will close the window and any changes made within the window will be
disregarded by the program.
Graph Menu Items
The Menu Items allow the user to
access the functions of the MSA. The Menu Items depend on the
topology of the MSA and the present Mode of operation. I expect
Menu Items to be added and expanded
with future versions of software.
[File]
[Save Image]
This will save the
contents of the graph window as a bitmap file. You will be given an
opportunity to name the file. The bitmap will contain the graph window
contents exactly as shown on screen. Be sure the window is fully
visible before you select
this menu item. The file is created by Liberty Basic, and some graphics
programs, will not recognize its format.
[Save Prefs] This will save all of the
existing parameters of the MSA into a text file. You can name it
anything but retain the .txt extension. Do not name it
"Prefs.txt" unless you want to delete the existing start-up
parameters. I suggest saving it in the default "MSA_Prefs" Folder.
[Load Prefs] The MSA opens
using the Prefs.txt file. You can load a different Preference
file that has been saved from a previous session.
[Save Debug File] This is
a
special feature for trouble shooting a faulty MSA. There is much
more work to be done in the area but it is designed to be used by me or
another MSA builder to help the user with problems. Basically,
the user would configure his MSA into a problem condition. He can
then click "Save Debug File" and name it
"pleasehelpme.txt". The helper can then send this file to me or
another helper. We can convert the file to allow our MSA's to
run, using this file. This is not fully active yet. I will
update
this paragraph when it is.
[Edit]
[Copy Image]
This
will copy the contents of the graph window to the clipboard, so you can
paste it into another application. The clipboard will contain the graph
window contents exactly as shown on screen (except the cursor will not
be captured), so be sure the window is fully visible before you select
this menu item.
[Options]
[Markers]
This will open a "Marker Options"
window. More will be written on this window at a later time.
[Sweep] This will open the "Sweep Parameters"
window. Same as double left clicking below the graph to open the
window.
[Show Variables] This will open a "Variables
Window" on the right
side of the Graph Window. It will contain many of the variables,
and
their values, that are used in the program. All data is relevant
for the step at which the sweep was Halted or for the step at which the
Left Mouse button is double clicked. The sweep can be resumed
with the Variables Window open and the data will update
with each step. However, the Variables Window may become hidden
behind the Graph Window. To view, go to the Windoze bottom tray
and click the Variables Window Tab. The topology of the MSA will
determine if the varaibles' values are valid.
These are the variables displayed in the Variables
Window:
this step = step number
of the sweep
dds1output = output frequency
of DDS 1
LO1 = output frequency of LO 1
or VCO 1
pdf1 = phase detector frequency
of PLL 1
ncounter1 = RF
divide ratio of PLL 1 (pdf1 = LO1/ncounter1)
Bcounter1
= divide
ratio of B counter inside
PLL 1
Acounter1 = divide ratio of A counter inside
PLL 1
fcounter1
= fractional divider of
PLL 1, but only if it is a Fractional N PLL, otherwise it is 0
rcounter1 = Reference clock
divide ratio of PLL 1 (pdf1 = dds1output/rcounter1)
LO2 = output frequency of LO 2 or VCO
2
pdf2 = phase detector frequency of PLL
2
ncounter2
= RF divide ratio of PLL
2 (pdf2 = LO2/ncounter2)
Bcounter2 = divide ratio of B counter inside
PLL 2
Acounter2 = divide ratio of A counter inside
PLL 2
rcounter2 =
Reference clock divide ratio of
PLL 2 (pdf2 = masterclock/rcounter1)
LO3 =
output frequency of LO 3 or VCO
3
pdf3 =
phase detector frequency of PLL
3
ncounter3 =
RF divide ratio of PLL 3 (pdf3
= LO3/ncounter3)
Bcounter3 =
divide
ratio of B counter inside
PLL 3
Acounter3 =
divide
ratio of A counter inside
PLL 3
fcounter3 =
fractional divider of PLL 3,
but only if it is a Fractional N PLL, otherwise it is 0
rcounter3 =
Reference clock divide ratio of
PLL 3 (pdf3 = dds3output/rcounter3)
dds3output =
output frequency of DDS 3
Magdata
= the actual bit count of
the Magnitude Analog to Digital Converter
magpower = the "processed"
power level of Magnitude
Phadata =
the
actual bit count of the Phase Analog to Digital Converter
PDM
= the state of the Phase
Detector Module, Normal is 0, Inverted is 1
Real Final I.F. = actual
frequency of the I.F., entering the Log
Detector
glitchtime = During
the first initial sweep after starting the program, the variable
"glitchtime" is given a value representing a relative
speed of the computer. A "glitchtime = 67.5675676"
means it will complete about 68 computer operations in one
millisecond.
Higher values will occur with faster computers. This value is
used in the MSA software to make all MSA's, somewhat uniform in speed.
[Setup]
[Hardware Config
Manager] This will open the "Configuration
Manager" window. This window will allow the
operator to modify any MSA default
value. A complete description for this window is in the section
"Initial Set-Up for MSA".
[Initial Cal Manager] This will open the "Calibration File
Manager" window for the user to calibrate the MSA or change values in the
calibration tables. A complete description for
this window is in the section "Initial Set-Up for MSA".
[Special Tests] This will open the "Special Tests"
window.
The window contains
provisions for testing various portions of the MSA. I will
later describe each of these in the paragraph, "Special
Testing
in
the Spectrum
Analyzer Mode".
[Data]
The following sub-menu items display data that can
be
copied and pasted into an external program for post processing and
evaluation. Many spreadsheet programs, such as Excel, can perform
some amazing signal evaluations. This is a very convenient method
for exporting data into those spreadsheets. The data are
displayed in a text format, within a Data Window. Each Data
Window has options for
Selecting and Copying. There are several items in the sub-menu,
but only those relevant during Spectrum Analyzer Mode will be described
here. I expect this to expand in future revisions.
[Magnitude
Input to MSA] - This will open a Data Window and display two
columns of values, with one row of values for each step, for one full sweep. These values
represent the Frequency and absolute power level of the input signal to
the
MSA. The values are in dBm, absolute. To be accurate, the
MSA must have been calibrated. This is a place holder and I have
a lot more work to do here.
[Magnitude
AtoD Bits] - This will open a Data Window and
display two columns of values, with one row of values for each step, for one full sweep. These values
represent the Frequency and Bit count of the Magnitude Analog
to Digital Converter. This is a place holder and
I have a lot more work to do here.
[Analysis]
[Filter]
This will open a "Filter Analysis" window for placing markers at
various points on the trace. More will be written on theis later.
[Mode]
[Spectrum Analyzer]
Spectrum Analyzer Mode
[VNA Transmission] Vector Network
Analyzer, Transmission Mode. Also known as "Forward"
measurements. For measuring S Parameters, S21 or S12.
Special Testing in the Spectrum
Analyzer Mode
This section
will describe special testing of the MSA while in the Spectrum Analyzer
Mode.
"Special Tests" window.
Click the menu item, Setup, and select Special
Tests. The "Special Tests Window" will open and display several
items. Only the items relevant to Spectrum Analyzer
Mode will be described.
Special Test: DDS 1
Control
"Command DDS
1"
button and box. The
data that is displayed in the box is the present output frequency of
the DDS. To command the frequency of DDS 1,
enter a new value
into the box, in MHz. Then click the "Command DDS 1" button. DDS 1 will immediately
command to the frequency value. You may use as many decimal
places as wanted, but the DDS output frequency will be rounded off to
about
14 millihertz. The value must be between 0
(MHz) and one half
the value of the DDS clock. If the
enterd data is outside these limits, and when the "Command DDS 1" button is clicked,
an error
will occur, and the program will halt. The DDS 1 output frequency
will remain at the new fixed frequency until the "Restart" button is
clicked, even if the Special Tests Window is closed. Therefore, if the sweep is
resumed by using the "Continue" or "One Step" button, the DDS 1
output frequency will remain at the fixed frequency and the sweep plot
will be altered.
"with DDS Clock at" box. The MSA Master Clock frequency is
displayed here. This is the true frequency
of
the DDS clock, which is also the Master Clock of the MSA (in MHz).
This may be changed by the
user. The actual Master Clock frequency is not changed, but the
software will use this new value for its DDS calculations. It
will take effect when either the "Command DDS 1" or "Command DDS 3"
button is clicked. This feature is used during the initial MSA
calibration for the Master Oscillator and is referred to in the
Calibration Procedure. The value will be used by the software
until the Special Tests Window is closed or when the MSA sweep is
restarted using the "Restart" button. It then reverts to the
default value that was preset in the Configuration Manager Window.
Special Test: DDS 3
Control
"Command DDS
3"
button and box.
This is an identical process of
"Command DDS 1" with an exception. The MSA sweep may be
re-entered by using the "Continue" or "One Step" button and the sweep
plot will not be altered. DDS 3 will remain at the fixed
frequency, and consequenctly, the Signal Generator or Tracking
Generator will be effectively "fixed" at a frequency that is determined
by DDS 3.
Special Test: DDS 3 as Tracking
Generator
"DDS
3 Track" button. By clicking this button, the
DDS 3 will
become a Tracking Generator for the Spectrum Analyzer. The DDS 3 output frequency will
track the Input Command
frequency of the MSA. It is limited to 0 MHz to 1/2 the Master Clock frequency,
nominally 0-32 MHz. The normal Tracking Generator
output becomes non-functional when the DDS 3 is tracking. Of
course, this test is valid only
if DDS 3 is installed. The Tracking Signal is accessed on the DDS
3 Module.
Follow
these steps for proper
operation:
Open the Sweep
Parameters Window, enter the wanted Center
Frequency, anywhere between 0-32 (MHz). Enter Sweep Width,
but make sure the sweep will not go below 0, nor above 1/2 the
frequency of the Master Clock. If either value is outside these
limits, the program will crash. Click Restart, then Halt the
sweep.
Open the Special Tests Window, click the "DDS 3 Track" button. DDS3 will immediately command to
the frequency that is displayed in the "This Freq" box. The
Spectrum Analyzer will begin sweeping when [One Step] or
[Continue] is pressed. If [Restart] is clicked, the sweep will
revert to it's normal operation. Therefore, to return DDS 3 as
a Tracking Generator, the "DDS 3 Track" button must be
re-clicked, and use only the [Continue] or [One Step] buttons.
Special Test: DDS 1 as Sweep
Generator
"DDS 1 Sweep" button. By clicking this button, the
DDS 1 will
become a Sweep Generator. The DDS 1 output frequency will
sweep, using the controls within the Sweep Parameters Window. It
is limited to 0 MHz to 1/2 the Master Clock frequency,
nominally 0-32 MHz. The normal Tracking
Generator
(Signal
Generator) during Spectrum Analyzer Mode remains functional.
Functions within the Spectrum Analyzer Mode and functions within the VNA Mode will be
non-functional. However, the Log Detector and A to D converters
remain functional.
Follow these steps for proper
operation:
Open the Sweep Parameters Window, enter the wanted Center
Frequency, anywhere
between 0-32 (MHz). Enter Sweep Width, but make sure the
sweep will
not go below 0, nor above 1/2 the frequency of the Master Clock. If either value is outside
these limits, the program will crash. Click Restart, then Halt
the sweep.
Open the Special
Tests Window, click the "DDS 1 Sweep" button.
DDS1 will immediately command to the frequency that is displayed in the
"This Freq" box. The MSA will begin sweeping when
[One Step] or [Continue] is pressed. If [Restart] is clicked, the
MSA
will revert to it's normal Spectrum Analyzer operation.
Therefore, to maintain DDS
1 as
a Sweeping Generator, the "DDS 1 Sweep" button must be re-clicked, and use only the [Continue] or [One Step] buttons.
--------
Special Test: Coaxial Cavity
Filter Sweep
There are no special buttons for
this test. It is a configuration set-up only. Command the
Center Frequency to 0 (MHz). Command Sweep Width (Span) to 20
(MHz). Remove the Final Crystal Filter and replace it with a
short length of coax.
--------
Using the Features of the Spectrum
Analyzer
This section is under construction.
Special Test for DDS 3 Crystal Filter
(Will be found on specialtests.html page, under construction.)
The
following is a procedure using the DDS 1
Sweep Generator to test the DDS 1 crystal filter:
(Will be found on
specialtests.html
page, under
construction.)
II. Initial Set-Up for
MSA
A. MSA
Software
Download and Installation,
The MSA software is written in Liberty
Basic and is, as
the
name implies,
Basic. I won't get into the total capabilities of
Liberty Basic,
you can get their application software and information at their
website. Find
it at
http://www.libertybasic.com. It is free, but will continually
"Nag" you to buy it.
Before MSA Software version 113, the MSA software
was released as a
".bas" file to be opened, manipulated, and run, using the Liberty Basic
Application Software. It will continue to be released as spectrumanalyzer.bas and requires that it be run using
Liberty Basic, version
4.03.
With the
revision 113, and all future
revisions, the MSA
software is also released as an Executable Program. That
is, the MSA software can be run on any Microsoft Windows computer,
without having to download any version of Liberty Basic. This was
a milestone event in the MSA progression.
MSA Software for Liberty Basic Users
If you
plan to run the MSA
software using Liberty Basic, read ReadMe114.txt before
downloading
the appropriate
files.
To
download any of the following
files, "Right
Click" your
Mouse and follow Windows instructions.
spectrumanalyzer.bas
(Revision 114) This is the MSA program
code, written in Liberty Basic, version 4.03. It can be viewed
with any text program on your computer, such as Word or Notepad.
It will "Run" with Liberty Basic version 4.03,
or higher.
ReadMe114.txt
Software release notes, and will be updated with
future releases.
Redist.zip
Folder with new Ntport.dll and
Zntport.sys,
required by Version 114.
MSA Software for Users without Liberty Basic
This executable
program
requires that you download all files and install them into a common
folder, namd
"MSA_Software". All
the files within the MSA Software folder must remain together, with
the exception(s) noted in
the file called ReadMe114.txt . Read this before
downloading the files. It explains the full
software installation procedure.
To download any of the following
files, "Right
Click" your
Mouse and follow Windows instructions.
spectrumanalyzer.tkn
(Revision
114) This is the MSA program
code that
has been "tokenized",
meaning, it is "pre-assembled".
spectrumanalyzer.exe
The Executable, that "Runs" the .tkn file
ReadMe114.txt
Software release notes, and will be updated with
future releases.
vbas31w.sll
Support File required by
Microsoft
Windows to run the executable.
vgui31w.sll
Support File required
by Microsoft Windows to run the executable.
voflr31w.sll
Support File required by
Microsoft Windows to run the executable.
vthk31w.dll
Support File required by
Microsoft Windows to run the executable.
vtk1631w.dll
Support File required by Microsoft
Windows to run the executable.
vtk3231w.dll
Support File required by Microsoft
Windows to run the executable.
vvm31w.dll
Support File required by
Microsoft Windows to run the executable.
vvmt31w.dll
Support File required by
Microsoft Windows to run the executable.
Redist.zip
Folder with new Ntport.dll and
Zntport.sys, required by Version 114.
Future
Updates and Releases
Usually, once the Support Files are downloaded
and installed, they will not need downloading
again. All future MSA software updates will be released as a
revision to "spectrumanalyzer.bas" and "spectrumanalyzer.tkn".
Simply, download either and replace your previous version
with the
latest revision. The name of any revision will always
remain "spectrumanalyzer".
It is important that this name never be changed. All software
changes will include a "ReadMe" text file with an appropriate revision
number.
Reverting
to Original Software
It is possible,
although unlikely, that you could manipulate the software
configurations into a condition where your MSA does not operate.
You can always revert to the original
software, and start over. Do this by finding and opening the MSA
Software folder. Click and highlight the folder named,
MSA_Info. Either, delete this folder and send it
to the computer's "trash can" or, change its name to "errorMSA_Info". Then open and run spectrumanalyzer.exe (or spectrumanalyzer.bas for Liberty
users) and
start
over
from scratch.
Previous versions of MSA Software
The previous versions of MSA software are not
maintained. However, I will keep them available on the MSA
Archives Page (in work).
Other "Executable" Software
The file called "spectrumanalyzer.exe" is a Runtime
Engine created by Liberty Basic. Normally, when it is "Run" it
looks for a file called, "spectrumanalyzer.exe", and runs
it. This Runtime Engine can run any Liberty Basic tokenized file,
but only if
the tokenized file is "directed" to run with the "spectrumanalyzer.exe". For
example, if you try to open and run "George.tkn",
Windoze will ask you what program do you want to "open with".
Tell Windoze to use "spectrumanalyzer.exe" for all
files that use the .tkn suffix. I expect to release several
different tokenized programs in the future.
B.
Hardware Configuration
MSA Hardware
The
SLIM MSA design has only one
mechanical adjustment, tuning of the Cavity Filter.
SLIM Modules, used in the MSA, have no mechanical adjustments.
The Original MSA has modules which need preliminary adjustments
before running for the first time:
For the original 8 Bit parallel A/D, adjust both pots to the
centers.
For the original 12 Bit parallel A/D, adjust both pots to
the centers.
For the original 16 Bit serial A/D, adjust both pots to
the centers (2.5 volts).
For the original Master Oscillator, adjust pot for
oscillator Vcc = 5.0 volts.
I will update this section more
extensively, for the Original MSA.
Computer Configuration
Some day, the MSA will be controlled by either the
Parallel LPT Port or by USB. For now, only Parallel control is
available. You may not have to make any configuration changes to
your computer for proper operation of the MSA. However, if your
computer has an extremely high speed processor or its PCI bus speed is
very fast, you may have to re-configure your LPT port. This is
how you do it:
Enter your computer's BIOS. This is normally
done from a cold start. I have to press the "DEL" key while the
computer is booting. Find your configuration for the LPT
Port. Depending on your computer, your choices will be Normal,
SPP, ECP, EPP, Bi-Directional, EPP+ECP, etc. For a moderate to
slow computer, any of these modes should work for MSA. For high
speed computers, select EPP. Save, and allow the computer to
continue its boot.
For Win XP users, see the XP
Problem at the end of this page.
C.
Software Configuration
The MSA
software is written with defaults to
"assume" that the MSA hardware topology is a SLIM MSA/TG/VNA. The user must be able to change
some of
the variable values in the software, to match the
topology of the user's MSA. The user can control this with the
Configuration Manager Window.
Open and Run
spectrumanalyzer.exe by double clicking it. When spectrumanalyzer.exe is run
for the first time, the Configuration Manager Window will open automatically. If not, it can be opened
from the Menu Item, "Setup". The variables that are
initially in place are defaults
for a SLIM MSA, with Tracking Generator and VNA.
Configuration
Manager Window
The variables that are
in this Configuration Manager Window are
for the first Verification SLIM MSA, with Tracking Generator and VNA. You must change the values
in your Window to match the topology of your particular MSA.
If
you have followed a standard build for the SLIM MSA, using SLIM
modules, then, for initial configuration, you need only to:
(1) click "Delete TG" if you did not install the tracking generator
feature, or
(2) click "Delete VNA" if you installed the TG but did not install the
Phase Detector Module, and
(3) select your ADC if it is not the 16-bit module, and
(4) enter the information for nominal frequency and bandwidth of your
final IF filter(s).
(5) click "Save Configuration"
In later calibration procedures you may
determine
more precise values for the items, and can change them by accessing
the Configuration Manager.
Each of the
following variables has an
explanation for its value. SLIM defaults are underlined.
PLL 1 Type - Select for LMX2325, LMX 2326,
LMX 2350, LMX 2353, ADF 4112
PLL 1 Polarity - For
non-inverting loop filter, use (non-inv). For inverting op amp, use
(invert)
PLL 1 Reference - The
value will determine the approximate Reference phase
detector frequency of PLL 1.
If the DDS 1 Center Freq is 10.7 and if DDS 1 Bandwidth is
greater than .010
(MHz),
then enter .974.
For other
topologies, this number can get rather involved. There are
several factors that determine the value to be used. It can
be determined by using
the following formula: PLL1 Reference = (VCO 1 minimum
frequency) x (DDS 1 Bandwidth)/(DDS 1
Center Freq). But, in cannot be greater than 1.02 (Mhz).
PLL 1 Mode - (Integer) or (Fract)ional
Mode. Use Fractional Mode only when using Fractional N type
PLL's. (LMX 2350, 2353). Even if using a Fractional N PLL, I
recommend using the Integer Mode for the MSA. It is less noisy.
PLL 2 Type - Support
for LMX2325, LMX 2326,
LMX 2350, LMX 2353, ADF 4112. The selection of "0" is
reserved for topologies that use a frequency multiplier scheme to
replace PLL 2.
PLL 2 Polarity - For
non-inverting loop filter, use (non-inv). For inverting op
amp, use
(invert)
PLL 2 Reference - The
value will determine the approximate Reference phase
detector frequency of PLL 1. Use 4 for most MSA topologies.
If PLL 2 is used in the Original MSA with
Original Tracking Generator (PLL3 is a fixed frequency), I suggest you
contact me for more
information. This value can get extremely involved.
PLL 3 Type - Support for
LMX2325, LMX 2326,
LMX 2350, LMX 2353, ADF 4112
PLL 3 Polarity - For
non-inverting loop filter, use (non-inv). For inverting op amp, use
(invert)
PLL 3 Reference - The
value will determine the approximate Reference phase
detector frequency of PLL 3.
The SLIM MSA uses .974.
If PLL 3 is being steered by DDS 3 then use the same rules as for PLL
1 Reference. If PLL 3 is a fixed frequency, as used in the
Original MSA with Original Tracking Generator, I suggest you contact me
for more information. This value can get extremely involved.
PLL 3 Mode - (Integer) or (Fract)ional
Mode. Use Fractional Mode only when using Fractional N type
PLL's. (LMX 2350, 2353).
DDS 1 Center Freq - The
value (in MHz) is the center frequency of the DDS 1 crystal filter. 10.7
DDS 1 Bandwidth - The
value (in MHz) is the bandwidth of the DDS 1 crystal filter. .015
DDS 1 Parser - Select the
command mode for DDS 1, (serial)
or (parallel)
DDS 3 Center Freq - The
value (in MHz) is the center frequency of the DDS 3 crystal filter. 10.7
DDS 3 Bandwidth - The
value (in MHz) is the bandwidth of the DDS 3 crystal filter. .015
LO 2 (MHz) - This is the fixed
frequency of Local Oscillator 2. Generally, it is 1024.
If PLL 2 is used in the Original MSA with
Original Tracking Generator (PLL3 is a fixed frequency), I suggest you
contact me for more
information. This value can get extremely involved.
If PLL 2 is
replaced with a multiplier scheme (PLL2 = 0), this value needs to be a
whole
number multiple of
the Master Clock nominal value.
Mast Clock (MHz) - enter
the exact frequency of the Master Oscillator (in MHz).
If the Master Oscillator Module is adjustable, enter the oscillator's
nominal value (64.0
in this case). If it is not
adjustable, enter the
actual frequency that the clock is creating (in
MHz). If you are not sure, enter the nominal value of the Master
Oscillator,
and you can
change this value during calibration. My Mast Clock is =
63.9995093
(a .3 Hz resolution)
The following defaults have been removed from the Configuration Manager
in version 114:
Sweep Center (MHz)
Sweep Width (MHz)
Top Ref
Bottom Ref
Wait
GlitchTime
Sig Gen Preset
Track Gen Offset
Max PDM out - VNA only.
This is the Bit Count output of the Phase Analog to Digital Converter
when the Phase Detector Module is reading 360 degrees. For the
SLIM Phase Detector Module and SLIM AtoD Module, this value is fixed
(either 65535 for the
16 Bit or 4095 for the 12 Bit). For the Original MSA using the Original
AtoD this value is adjustable, and is determined during calibration
(use 65535, 4095, or 255 for the 8 Bit).
Inv Deg - VNA only. Inversion
in Degrees. This is the actual amount of phase change when the
Phase Detector Module has its state changed from Normal to
Inverted. A perfect PDM would have a 180 phase change. The
actual value is determined during the PDM calibration.
ADC type - Select 8(orig
8-bit), 12(ladder), 16(serial
16-bit), or 22(serial 12-bit). It is assumed that the same
type ADC is in both the Magnitude and Phase AtoD Converter Module.
TG Topology - Select (orig)inal
TG or (DDS3/PLL3)
Control Board - Select
(old) for Original Control Board, or (SLIM original) for the
SLIM Control Board. There is another option (Old, new
harness). This is a place holder for an in-work design of a
wiring harness to convert the Original Control Board and original
modules to take advantage of new software changes. At this time,
I see no advantage, so I may delete this option.
LPT Port Address - For every
home computer I have seen (so far) the address is Hex 378. If your
computer does not command the MSA, this may be the problem and needs to
be changed.
List your final filters:
This is a table listing of Resolution filters that are installed in the
MSA. At this time a maximum of 4 filters (and Paths) are
allowed. I will work on a scheme to use a maximum of 16.
The original default is a single filter Path with frequency 10.7
and bandwidth 15.
To change this default to match your
final filter, highlight the data by clicking it with the
Mouse. Four Buttons will appear: AddPrior, AddAfter,
Delete, and Replace
Enter the correct data for your Path 1 filter in the
Freq(MHz) box and BW(KHz) box. Then click the Replace
button. If you use more than 1 Resolution filter, then enter the correct
data for your next filter in the Freq(MHz) box and BW(KHz) box.
Then click the AddAfter button. This will become Path 2.
If you use a 3rd Resolution filter, then enter the correct
data for the filter in the Freq(MHz) box and BW(KHz) box. Then
click the AddAfter button. This will become
Path 3.
If you use a 4th Resolution filter, then enter the correct
data for the filter in the Freq(MHz) box and BW(KHz) box. Then
click the AddAfter button. This will become
Path 4.
The Buttons in the upper right
quadrant have these functions:
Set to SLIM Defaults - This
will insert all SLIM defaults into the Configuration Manager
Window. Upon Initial Set-Up, the default
values are
already inserted. But, if
the Configuration Manager Window is opened after the Initial
Set-Up,
it is a quick way to change all the values back to SLIM defaults.
Re-Load File - This will read
the hidden config.txt file and enter its values into the Configuration
Manager Window. Upon initial set-up, that file does
not exist. Therefore, this button is only used after
the initial set-up and first run.
Delete TG - This will delete
all options in the Configuration Manager Window, that
pertain to a Tracking Generator. Click this if you do not
have the Tracking Generator installed.
Delete VNA- This
will delete all options in the Configuration
Manager Window, that pertain to the Vector Network Analyzer.
Click
this if you do not have the VNA installed.
Help - This will open a window
for more explanations. I will add more to this window.
Save Configuration - If this is
the Initial Set-Up for the first time, this button will save the
entries into the config.txt file, the Configuration Manager Window will
close, and return to the
main program. When the Configuration
Manager Window is opened in subsequent runs, this button will just save
the entries into the config.txt
file.
Return to MSA Without Saving -
This button does not appear on the Initial Set-Up. Subsequently,
this will just close the Configuration Manager Window and return
to the main program, without saving the entries.
Save
the Software Configuration.
After the
configuration values are entered, click
the Button called "Save Configuration". The Configuration Manager Window will
close, and the Working
Window and Graph Window will open. The
MSA will begin
sweeping in the Spectrum Analyzer Mode.
You will notice that this Graph Window is
showing a much different
display than the Graph Window shown earlier on this page. This
graph
is more likely what you will see during the Inital Set-Up. The
cavity
filter is not tuned, the Master Oscillator is not calibrated, and the
Final Crystal Filter (Resolution Filter) is not exactly as
planned. The power measurements are likely to be incorrect, since
no magnitude calibrations have been performed. We will perform
those calibrations in the following steps. You can verify that
Path Calibrations and Frequency Calibrations have not been performed by
opening the Calibration File Manager Window. Open it by
selecting, from the Graph Menu, Setup, Initial Cal Manager.
Calibration File Manager
Window
Calibrations are performed with the use of the Calibration
Manager.
The Calibration Manager creates and controls all of the Calibration
Files that are used by the main MSA Program. During the Initial
Set-Up and Running of the MSA Program, Calibration Files are created
and filled with SLIM MSA default values. The user has the option to change
any, or all of these values, by using the Calibration Manager. To
access the Calibration
File Manager Window, select from the Graph Menu, Setup,
Initial Cal Manager.
*The right hand "Available Files" menu will display all of the MSA's
Calibration
files.
*The
Calibration
Manager will control these files:
* The Frequency Calibration File.
* A Path Calibration File, for
Path 1. There may be up to three more Path Calibration Files,
depending upon
the number of Paths, as entered during the Initial Configuration
Managment
Procedure.
*Within
"Available
Files" menu, the 0(Frequency) is
highlighted. This is an opening default.
*The left text box is named "Frequency Calibration
Table", and will display the most recently
saved
Frequency
Calibration File.
*Within "Available
Files" menu, select and highlight 1(xxx yy)
*The left text box is named "Path Calibration
Table", and will display the most recently
saved Path 1
Calibration File.
Buttons
and Boxes:
Clean Up - This will sort the
displayed Table's Calibration values.
Display Defaults - This will
change the displayed Calibration values to the nominal SLIM defaults.
Re-Load File - This will load
the last saved MSA Calibration Table values into the displayed table.
Save File - This will replace
the MSA Calibration Table with the
displayed Table's Calibration values.
Return
to MSA - This will close
the Calibration
File Manager Window and give the option to Save.
Start Data Entry - This will
allow the user to Calibrate the MSA,
semi-automatically. When clicked, more boxes and buttons will
appear, depending on the type of calibration requested. These
will be described during the Calibration Procedures.
III.
Calibration Procedures for the MSA
The MSA can be
constructed with a variety of
topologies. There are no two
MSA's that
have identical characteristics.
The purpose of calibration
is to measure, characterize, and quantify the effects of those
characteristics. Once calibrated, an MSA can
perform with the accuracy of an
expensive, commercial unit. These are the main factors that
affect MSA measurement accuracy:
* The coaxial cavity filter affects the gain/loss characteristic
of the MSA. It is sensitive to its source and load impedance,
and will need tuning, even if pre-tuned
independently from the MSA. This is accomplished in the Coaxial
Cavity Filter, Tuning Procedure.
* The Master Oscillator
determines the frequency accuracy of the
MSA. It is usually quite stable, once it reaches its operating
temperature, but may not be absolutely accurate. The
software can be compensated for this inaccuracy. This is
determined in Master
Oscillator Calibration.
* The Resolution Bandpass
Filter(s) may not be exactly at the
expected center frequency. However, it can be charcterized, and the software can be
compensated. This is accomplished in Resolution
Bandpass Filter Calibration.
*
MSA Magnitude Measurement is, basically, a linear function of input
power. MSA linearity is quite good
in most of its dynamic range, but deviates significantly
when its
input power is close to its upper and lower dynamic range limits. All
magnitude nonlinearity can be characterized and compensated by
software. Magnitude nonlinearity is characterized in Path Calibration for Magnitude and Phase.
*
MSA Magnitude
Measurement is affected when using different Resolution Bandpass Filters. This is due to
different insertion losses and filter bandwidths. Therefore, the
MSA gain can be characterized for each Resolution Bandpass Filter that is
used. Gain is characterized in Path
Calibration for Magnitude and Phase.
*
MSA Magnitude Measurements are affected by frequency changes within the
MSA. There are multiple components in the MSA whose gain/loss
characteristics change when frequency changes. MSA gain can
change greater than 2 dB over the frequency range of 0 to 1000
MHz. These gain vs. frequency changes can be characterized and
compensated by software. Magnitude Accuracy versus Frequency is characterized in the Frequency Calibration for Magnitude.
*
MSA/VNA
Phase Measurement accuracy is affected by the power of
the input signal and the frequency of operation. The Phase Accuracy versus input
signal power level is characterized in Path
Calibration for Magnitude and Phase.
*
MSA/VNA
Phase Measurement accuracy is affected by the frequency at which the
MSA is operating at. The Phase Accuracy versus
Frequency is characterized during normal VNA operation each time a Line Reference Calibration is
performed. But, a one-time VNA Baseline Calibration is performed to provide a coarse
calibration for "uncalibrated" VNA operation.
The measurement accuracy of the MSA can be optimized
by adding a permanent, 50 ohm attenuator on the input of the MSA.
The best value can be determined by experimentation, but generally, a 3
dB to 10 dB attenuator is best. If you plan to use a permanent
"pad", such as a 10 dB, you should have it attached during the
Calibration procedures. Padding the MSA does not change its
dynamic range, but it does shift it in the positive direction.
Example: Range without: -20 dBm to -110 dBm, Range with: -10 dBm to
-100 dBm. The same consideration can be made for the output of
the Tracking Generator. Its output will decrease by the amount of
padding placed on its output connector. I have determined that 8
dB of padding on both the TG output and the MSA input is optimum.
Your MSA would be similar, if built according to the SLIM design.
A. Coaxial Cavity Filter, Tuning
Procedure:
This is not really a
"calibration"; it is a tuning procedure. If the coaxial cavity
filter has been pre-adjusted, with the
mechanical information given in the construction procedures, it will
be fairly close. For correct adjustment, perform the following
steps. No other test equipment is required.
* Open
and Run
the MSA Program (spectrumanalyzer.exe).
* Halt the sweep
* Open the Sweep Parameters Window
* Select the Video
Filter BW to Wide
* Assure Final Filter Path 1 is selected, if not
select Path 1
* Verify, "0" as the Center
Frequency, "Cent" box.
* In the
Span Box, enter 10 times the
bandwidth of the Final Crystal Filter (in MHz).
* Click "OK",
then
"Restart". The
Graph
should show a response curve, even if the cavity filter is
badly
mistuned. It is also possible that the response is below the
Bottom
Reference Line. If so,
Halt sweep and change "Bot Ref"
box
to -120. Click "Restart".
* It is very likely that the center
of the response
curve will not be in the center of the
Graph. To
center it, Halt the sweep. Place Mouse pointer over
the center of the response curve and Left
double click the mouse.
Click
"Mark->Cent" button. Click "Restart". The
response will now
be in the center of the Graph.
* Adjust
the tuning of the Cavity Filter for maximum amplitude response (maximum dBm). The response should look
more like the Graph
Window near the top of this page.
* For more critical tuning, perform
the following
extra steps:
* Halt sweeping
* Open the Sweep Parameters Window
* Change Span to "0"
* Enter 300
into "Wait" box
* Select the Video
Bandwidth to Wide.
* Click "OK", then "Restart".
* Halt sweep.
* Select from Menu, Options,
"Show
Variables". The "Variables" Window will open.
* Click "Continue". The
sweep will be
very slow and the variable, Magdata = xxxxx will update and display the
Bit Count value of the Magnitude. Tune the Cavity Filter for
maximum Bit Count.
* Tuning is complete. Halt the sweep.
Close the Variables Window, if open.
B. Master Oscillator Calibration:
If your system is the Basic MSA, and has no Tracking
Generator, use Method A. If your MSA has the Tracking Generator
addition, with or without VNA extension, use Method A or Method B.
Method A. For the Basic
MSA (no Tracking Generator). Beat
Frequency Method.
This method requires an external AM radio receiver
(and appropriate antenna)
that will
recieve WWV at 2.5 MHz, 5 MHz, 10 MHz, or 20 MHz. This is for
North America. For Europe or other countries, you can use a
Frequency Standard radio station, operating below 32 MHz.
The DDS 1 spare signal is used as a "beat" frequency oscillator.
1. Tune
the external receiver to WWV, 10 MHz. Use an antenna, if
necessary. I
will use 10 MHz during this procedure, but others may be used.
2. Open and Run
the MSA Program (spectrumanalyzer.exe). Halt the
sweep.
3. Connect a length of hook-up
wire to the DDS 1 spare output, and position the wire close to the
radio reciever or antenna input. If the MSA's
DDS 1 spare output is brought out to the front panel, the center
conductor of the hook-up wire should fit snuggly in the center pin of
the connector. If the DDS 1 spare output is not brought out, it
is available on the bottom of the SLIM-DDS-107 and is J3. Use a
hook-up wire size so that its center conductor will fit snuggly in the pwb hole.
4.
(allow
the MSA to warm up for 30 minutes). Select from Menu,
Setup,
"Special Tests". In the Special Tests Window, enter 10 (MHz, the
frequency
of WWV) into "Command DDS 1" box . The "with DDS Clock at"
box will display the value of the default global variable,
"masterclock" (64.xxxyyyz). Click the "Command DDS 1"
button. DDS 1 will immediately command to
approximately "10" MHz. The program software used the value in
the "with DDS Clock at" box as "masterclock" for
its calculation. Leave the Special Tests
Window open.
5. Couple the DDS 1 spare output
wire
close to the
receiver to
obtain
an audio beat signal. If the DDS 1 and WWV frequencies are more
than a few hundred Hz apart, this "beat" may sound like a tone.
For best results, the WWV input power to the radio reciever and the DDS
1 signal input power to the radio reciever should be equal. Move
the DDS 1 signal wire to a location near the radio to obtain best
results.
6. To adjust the Master Oscillator
for
zero beat, use a. or b.
a. If you have a
mechanical
adjustment for the master oscillator, the nominal Master Oscillator
frequency
value should be in the "with
DDS Clock at" box. If not, Halt the sweep and enter it, then click
the "Command
DDS 1" button.
Manually
adjust the Master Oscillator
for zero beat. A final zero beat is less
than 1 noticeable cycle per second. When found, you are finished. Skip
b.
b. If you don't have a mechanical adjustment for the
master oscillator, zero beat is found by changing the value in the "with
DDS Clock at" box and clicking the "Command
DDS 1" button. The
goal is to find the lowest frequency zero beat.
If the beat frequency increases when changing values, you are changing
in the wrong direction. When the final value in the "with
DDS Clock at" box is determined, you are finished.
7. Exit
the
Special Tests Window.
8. From the Graph Menu, select Setup, Hardware
Configuration Manager.
9. In the Configuration Manager Window, change
the "Mast
Clock" to
the final value that was
entered in the "with
DDS Clock at" box.
10. Click the "Save Configuration"
Button.
The MSA program will close.
If a
zero beat to within 1 cycle per second can be obtained, the Master
Oscillator is calibrated to within 1 part in 10 million, (using WWV,
10 MHz). If WWV, 5 MHz is used, the calibration is within 1 part
in 5
million, etc. This is
a
one-time calibration.
Method B. For the MSA
with Tracking Generator or VNA. This is a Beat Frequency Method, but no
external receiver is required. The MSA acts as a receiver.
This
method requires that the cavity filter be adjusted first.
Otherwise, there may not be enough signal to perform the calibration.
This method uses the MSA as a radio reciever for WWV
at 2.5 MHz, 5 MHz, 10 MHz, or 20 MHz. This is for
North
America. For Europe or other countries, you can use a Frequency
Standard radio station, operating below 32 MHz. DDS 3 is used as the "beat"
frequency oscillator.
1.
Connect an
antenna or long wire into the input of the MSA. This injects WWV into the
MSA.
2. If the MSA program is not running,
RUN
the program.
3. Halt the sweep.
4. Open the Magnitude Axis Window
5. Enter "-20" into the "Top Ref"
box. Enter "-120" into the Bot Ref" box.
6. Click "OK", "Restart", then "Halt"
7. Open the Sweep Parameters Window
8.
Command the MSA Center Frequency to WWV, 10 MHz., "Cent" box = 10.0
I
will use 10 MHz during this procedure, but other WWV's may be used.
9. Uncheck the "Refresh Screen Each Scan"
10. Click "OK", then "Restart".
11. Verify the signal response is in the
center
of
the Graph. If not, Halt and center the signal. Click
Restart. Allow
the MSA to warm up for at least 30 minutes. The Master Oscillator
should stabilize in this time period.
12. Verify the input signal
level has at least 10 dB of signal to noise ratio. Take note of
this
input power level, as WWV power. Example, -90 dBm.
13. Halt
the sweep.
14. Open the Sweep Parameters Window
and enter
"0" into the "Span" box.
15. Click "OK", "Restart", then "Halt"
16. Open the Magnitude Axis Window and
enter
"-70" into the "Top Ref" box. Enter "-110" into the "Bot Ref"
box. (use +20 dB
above and -20 dB below the
noted WWV power).
17. Click "OK" then "Restart".
18. A uniform, horizontal,
trace
will be displayed, along with some noise ripple. Some magnitude
change will occur if the WWV
signal is fading or modulating.
19. Halt the sweep.
20. Select from Menu,
Setup,
"Special Tests". In the Special Tests Window, enter 10 (MHz, the
frequency
of WWV) into "Command DDS 3" box . The "with DDS Clock at"
box will display the value of the default global variable,
"masterclock" (64.xxxyyyz). Click the "Command DDS 3"
button. DDS 3 will immediately command to
approximately "10" MHz. The program software used the value in
the "with DDS Clock at" box as "masterclock" for
its calculation. Leave the Special Tests Window open.
21.
Combine both the DDS 3 spare output signal, and the antenna input,
using a "T" connection on the input to the MSA.
For best results, the WWV input power to the MSA and the DDS 3
signal input power to the MSA should be equal. See a. and b. next.
a. If the MSA's DDS 3 spare
output
is
brought out to a front panel coaxial connector, its power level is
very high, about -8 dBm. Add an appropriate attenuator so that
the DDS 3 power into the MSA is approximately equal to the level of the
WWV signal.
b. If
the DDS 3 spare output is not connectorized, it is available on the
bottom of the
SLIM-DDS-107 and is J3. Use a hook-up wire with a
center
conductor that will fit snuggly in the pwb hole.
The end of the wire can be loosely coupled to the WWV antenna input to
the MSA, so that its power level is somewhat equal to the WWV power
level.
22. Click
"Continue". The
previous uniform magnitude trace will look like waves on water.
These waves are a result of the beat frequency between WWV and DDS
3. There could be many "waves" per sweep, meaning the Master
Oscillator is far off frequency. You can "grab" and move the
Special Tests Window out of the way to see the Graph display.
23.
Adjust the Master Oscillator for zero beat, use a. or b.
a. If you have a
mechanical
adjustment for the master oscillator, the nominal Master Oscillator
frequency
value should be in the "with
DDS Clock at" box. Example, "64.00". If not, Halt.
Enter the correct Master
Oscillator value, then click
the "Command
DDS 3" button, then click "Continue". Manually
adjust the Master Oscillator
for zero beat. Zero beat occurs when the
"waves" occur very slowly (less than one per second). The sweep
can be slowed for better display of the very slow waves. Halt
the sweep, enter "20" into the "Wait" box, "Continue". When this
adjustment is found, you are
finished. Halt the sweep and skip the
next step b. I have a mechanical adjustment in my Original
MSA. It is very easy to adjust to 1 wave (1 beat) every 5 seconds.
b. If you don't have a mechanical adjustment for the
master oscillator, zero beat is found by changing the value in the "with
DDS Clock at" red box. The
goal is to find the lowest frequency zero beat.
If the beat frequency increases when changing values, you are changing
in the wrong direction. The procedure is: Halt the sweep, change
the value in the "with
DDS Clock at" red box, then click the "Command
DDS 3" button, then click "Continue". Repeat, until the value of "with
DDS Clock at" red box creates the slowest waves (less than one per second).
Halt the sweep. You are
finished. In the SLIM MSA, I was able to command the value of
the Master Oscillator until I got 1 wave (1 beat) every 3 seconds.
24. Exit the
Special Tests Window.
25. From the Graph Menu, select Setup, Hardware Configuration
Manager.
26. In the Configuration Manager Window,
change
the "Mast
Clock" to
the final value that was
entered in the "with
DDS Clock at" box.
27. Click the "Save Configuration"
Button.
The MSA program will close.
If a
zero beat to within 1 cycle per second can be obtained, the Master
Oscillator is calibrated to within 1 part in 10 million, (using WWV,
10 MHz). If WWV, 5 MHz is used, the calibration is within 1 part
in 5
million, etc. This is
a
one-time calibration.
C. Resolution
Bandpass Filter Calibration:
The center frequency of the Resolution Bandpass Filter (Final
Crystal Filter) may not be exactly as the manufacturer states.
For wide-band filters of 20 KHz or greater, this is not much of a
concern. But for narrow filters, this error will be indicated
when the swept response in not in the center of the graph, when it
should be. To determine the real center frequency of the Final
Xtal Filter, follow these steps.
1. The Master Oscillator must have been
calibrated.
2. Run
the MSA Program (spectrumanalyzer.exe).
3. Select Magnitude Video
Bandwidth to Wide.
4. Halt sweep.
5. Open the Sweep Parameters Window
6. Verify or change the MSA Center
Frequency to "0", and Filter Path at P1
7. In Span box,
enter 5 times the bandwidth of the Resolution Filter in Path 1 (Final
XtalFilter)
8. Enter "20" into the "Wait" box
9. Click "OK" then "Restart".
10. The trace on the Graph is the actual
frequency response curve of the Resolution Filter. A perfectly
tuned Resolution Filter will have low ripple within the 3 dB bandwidth.
11.
Verify the response is centered. Centered, means that the 3 dB points
are equally distanced from the center of the Graph, and the maximum
power indication is in the center of the Graph.
12. If centered, verification is complete.
13. If the response is not centered, Halt the
sweep. Position Mouse pointer over the center of the response
curve. Double Left click or single Right click the Mouse.
The "L" marker frequency in the Marker Box will indicate the MSA tuning
frequency. A negative value is valid. We will call this
value, "L Mark
Freq".
14. To determine the true center frequency of the Resolution
Filter:
a. true center frequency =
value in "Select Final Filter Path:" box - "L Mark Freq"
b. example, if the "L" marker is at
0.0011 then true center frequency = 10.7 -
0.0011 = 10.6989 (MHz)
c. or, if the "L Mark Freq" was at
-0.0015 then true center frequency = 10.7 -
(-0.0015) = 10.7015
d. this "true center frequency" will be
entered into the Configuration Manager Window for Path 1
e. or, for subsequent Paths,
"finalfreq2", "finalfreq3", and "finalfreq4"
15. To determine the unknown Bandwidth of the
Resolution Filter:
a. With the sweep Halted, Select Marker "L". Position the Mouse
cursor directly on the trace that indicates the lower -3dB
point of the filter response curve. Double Left click the
Mouse.
The frequency will be displayed in the Marker Box as the "L" frequency.
c. Select Marker "R". Position the Mouse
cursor directly on the trace that indicates the upper -3dB
point of the filter response curve. Double Left click the
Mouse.
The frequency will be displayed in the Marker Box as the "R" frequency.
d. The actual Bandwidth of the Resolution
Filter is "R" frequency - "L" frequency.
e. This actual Bandwidth will be
entered into the Configuration Manager Window for Path 1
16. If
you have more than one Resolution Path, repeat steps 4 through 15 for
each Path (2, 3, 4).
17. In the Graph Window, select Menu
item, "Setup". Select Configuration Manager.
18. In the Configuration Manager Window,
change the global variable, "Mast Clock" to the final value that was
entered in the "with
DDS Clock at" box.
19. Click the "Save Configuration"
Button. The MSA program will close.
17.
Change the Path Variables in the Configuration Manager Window
a. If sweeping, Halt the sweep
b. Select Menu
item, "Setup", Configuration Manager.
c. In the Configuration Manager
Window, change the appropriate Filter Paths for correct frequency and
bandwidth.
d. Click the "Save Configuration"
Button. The MSA program will close.
e. You have completed Resolving the Resolution Filter Paths
D. Phase Detector Module Calibration
(VNA only):
The Phase Detector Module (PDM) is very accurate when the differential
phase of its two input signals is between +72 degrees and +288
degrees. If the differential phase
is outside these boundries, the PDM will automatically be inverted, and
a phase measurement is repeated. The inversion of a "perfect" phase
detector creates a 180
degree phase shift and an inversion could be compensated
by factoring out 180 degrees. But, the MSA's PDM is not
"perfect". We must calibrate the PDM to find
out what the real phase shift is when the PDM is inverted. This
real phase shift is found by using the following procedure:
Updated Aug 26, 2009,
Changed PDM Calibration Procedure (I goofed up in the original version,
and the software will give an error condition).
*
Open
and Run
the MSA Program (spectrumanalyzer.exe).
* Halt
sweep.
* Enter the VNA Transmission Mode
* Halt the sweep
* Allow
at least a 30 minute warm-up to ensure valid
measurements
* Select Menu, Operating Cal, Reference To,
and check "No Reference", exit References window
* Connect
Tracking Generator output to MSA input with 1-2 foot cable.
* Set the Phase Video Filter Switch to WIDE
bandwidth.
* Open the Sweep Parameters Window
* Select Video Filter BW box to Wide
* Select
Final Filter Path 1, if not already displayed.
* Enter
200 into "Cen" box, center frequency = 200 MHz
* Enter
200 into the "Span" box, sweep width will be 200 MHz
* Click
"OK" then "Restart".
* Verify
a sawtooth response.
* Halt
the sweep. The
Magnitude
power level will display the power level of the Tracking Generator and
is
not important, unless it indicates an unusual power level.
* Select
the "L" marker and position the Mouse cursor on the slope that is near
+90 degrees (left phase scale). Double Left click the
Mouse. The "L" marker phase is displayed in the Marker
Box. Reposition the "L" marker to obtain 90 degrees, if necessary.
* Click the"Mark->Cent" box.
* Click "Restart"
* The
sawtooth will shift with the "L" marker in the center of the Graph
* Halt
the sweep
* Set the Video Filter Switch to NARROW
bandwidth.
* Open the Sweep Parameters Window
* Change
the Span to 0 (MHz)
* Select Video Filter BW box to Narrow
* Click "OK", then "Restart"
* Both
the Magnitude and Phase traces will be horizontal lines.
* Halt
the sweep. Phase at the "L" marker should be approximately 90
degress. The Magnitude is not important.
* Select Menu, Setup, PDM
Calibration. The "PDM Calibration" window will open
* Click the "PDM Inversion Cal"
button. The following take place:
* the button will
change to "Be Patient". (This calibration takes about 10 seconds)
* the "Current Inversion =" will go
blank. It was displaying the current PDM calibrated value.
* the computer will command the PDM
to its uninverted state
* the computer will beep and
take the first phase measurement.
* in about 5 seconds the computer will command the PDM to
its inverted state
* the computer will
take the second phase measurement.
* when the measurements are
finished, the
computer will beep again
* the button will revert back to "PDM Inversion Cal"
* the software will calculate the PDM
Inversion Phase Shift, using the two measurements.
* the "Current Inversion =" will
display the newly calculated PDM
Inversion Phase Shift
* you should expect a value of 180 degress, plus or minus 5 degrees.
* The
Message Box will display the two phase values taken during the
measurement.
* You may repeat the measurements by
clicking the "PDM Inversion Cal" button as
many times
as you
wish. I suggest 4 or 5 times to verify repeatability.
* You may choose the save this new
value as the permanent PDM Calibration value, or
click the
"Cancel" button to exit without saving.
* For a permanent Calibration, click
the "Save New Value and Quit" button. This will install
the
value into the Configuration Manager file, automatically. The new
value will be valid for
this and
all future MSA sessions. If you wish to change the value
manually, open the
Hardware
Configuration Manager and change the value in the "Inv Deg" box.
* PDM Calibration is complete.
This is a one-time calibration and
should never have to
be repeated,
unless there is some future
modification to the PDM.
E.
Path Calibration for Magnitude (and Phase for VNA):
MSA
Magnitude measurement
is
a correlation between MSA input power and a binary (digital)
representation of
the converted input signal. Under ideal conditions, this
correlation
would be absolute, and dependent only on the total
gain/loss of the MSA. However, variation can be
expected, due to
these factors:
* Mixer 1 is non linear in its compression
range, but we can use this range if we quantify it.
* The Log
Detector, used to convert RF power to voltage, is non linear.
Close, but not perfect.
* The A to D Converter, used to convert Log Detector
voltage to binary bits, is not exact.
* MSA
gain/loss is dependent on the characteristics of each Resolution Filter
Path. Path losses can
deviate as much as 10 dB.
Even
with these contributing factors, "Correlated Input Power" can be
characterized. Path
Calibration will measure the correlations, at
different power levels, and record them in a "Path Calibration
File". This will be done for each different Resolution Filter
Path. There can be up to 4 Path Calibrations, each creating
its own "Path
Calibration File".
MSA/VNA Phase measurement
is
the phase difference between the MSA's converted input signal and an internal reference
signal. In an ideal VNA, the power
level of the input signal would have
no effect on phase measurement accuracy. However, the MSA is not
ideal, and has two main components that change phase when
power level changes.
They are, Mixer 1 and the Logrithmic Detector. This "Phase versus
Magnitude" change can be compensated for, if this change is
known. Path
Calibration will measure this phase change
versus power level change, and record it as the "Phase Error vs.
Magnitude"
Correction Factor. When the VNA is measuring input signal Phase,
it will access the Path Calibration File, take the Correction Factor
and subtract it from the Phase Measurement. The result is the
True Phase of the input signal.
During
a Path
Calibration, a signal with a known
power level is
injected into the MSA and the digitized Magnitude output is recorded.
This
input power level and digitized Magnitude output is installed
in its own "Path Calibration Table". If the MSA has the VNA
capability,
a digitized phase measurement is also installed in the same "Path Calibration Table". The input power is
then changed to another known power level (at the same frequency) and
the digitized output is also installed in the "Path Calibration Table". This process is repeated
for multiple input power
levels. The final accuracy of the MSA depends on the accuracy of
the known input signal level and the number of calibration points
taken. The more calibration points taken, the more accurate the
MSA becomes.
For an MSA with a dynamic range of 100 dB, and to be accurate to within .1
dB, a Path Calibration would require 1000 different input power
levels. The MSA can have up to four
Resolution
Bandwidth Filter Paths. This would not be
practical,
so each Path Calibration will calibrate 30 input power levels, or
less. During normal MSA Magnitude measurement, the software will
use these calibration points and use interpolation to find the closest
digitized magnitude.
Step
by Step Procedure for Path
Calibration:
Note: These calibration procedures must have been performed
before a Path Calibration.
Tune coaxial cavity filter
Master Oscillator Calibration
Resolve the Center Frequency of Path 1, and
others, if installed.
Phase Detector Module Calibration, if the MSA has the VNA installed.
1. Configure MSA for Path
Calibration:
a. Open and Run
the MSA Program (spectrumanalyzer.exe).
* Verify MSA is in
Spectrum
Analyzer Mode
* Halt the sweep.
b. Select Magnitude and Phase Video
Bandwidth Switches to Narrow.
c. Open Sweep Parameters Window and configure:
* Verify the Select Final
Filter Path box is Path 1
* Select "Narrow" in Video Filter BW
pull-down box
* Enter into the "Cent"
box, the
correct frequency
you are calibrating at. A Calibration
Frequency of 1
MHz is preferred, but, somewhere between 1 MHz and 2 MHz.
* Enter 0 into "Span" box.
* If your MSA
has the Tracking Generator Option, you may use it as the Calibration
source.
* If so click the "Signal Generator"
button to enter Tracking
Generator Mode.
* This will automatically command
the TG to the Calibration Frequency
* Click "OK",
then "Restart"
* Halt the Sweep
2. Configure the Calibrated Signal
Source MSA
a. Configure Signal Source
* For a Basic MSA (no
Tracking Generator), you must use an external CW Signal Source.
* Adjust the external CW Signal Source to the Calibration Frequency.
* Adjust the power level of the external
Source to
approximately, -10 dBm.
* Most MSA's will be in saturation
with an input of
-10 dBm. Therefore, higher
calibration levels are usually
unnecessary.
* For the MSA/TG (has
Tracking Generator), you may use the Tracking Generator as the
Signal Source.
* The output power level of the TG
is approximately -10 dBm
* Most MSA's will be in saturation
with an input of
-10 dBm. Therefore, higher
calibration levels are usually
unnecessary.
* If you need an input power higher
than -10
dBm, you will require an amplifier.
* For the very best Path Calibration
results,
connect the output of the Signal Source to a
low pass or band pass filter that will pass only the
fundamental calibration
frequency.
Harmonic effects are rather minor, but, a filter will
help. This is a user option.
b. Configure Step Attenuator
* Connect the Signal Source to the input
of a precision selectable attenuator. An ideal
attenuator would have 120 dB of range, with 1 dB resolution, and an
accuracy of .01 dB.
It
would also not deviate in Phase for any step change. For a Basic
MSA (no VNA),
Phase change
is not important.
* No matter what Signal Source you are using,
the
Calibration Power level injected on the
input connector of the MSA
must be
known, as accurately as possible. The final MSA
operating accuracy depends on the accuracy of the
Signal Source and attenuator.
*
Calibrate the Step Attenuator's Output with a precision power
measurement instrument.
* With the attenuator at 0 dB,
measure the Signal Power and record it.
__________dBm.
* This "Signal Power" value will be
used for each
Path Calibration. Example: -10.75
dBm.
* Precision power meters are not
available to
most people. But, a fair substitute is an
Oscilloscope with at
least 5 MHz bandwidth and a 50 ohm termination on its input.
For an o'scope reading, dBm = 20
x log(peak to peak volts / .6324555 volts)
* Connect the Step
Attenuator's Output to the input of the MSA.
c. Adjust the step attenuator for an output level of approximately, -30
dBm, +/- 5 dBm.
* It does not have to be exactly -30
dBm, but it does have to be accurately known.
* Whatever
the power level is, it must be known to within .1 dBm (.01 dBm is
preferred).
* This
power
level will be referred to as "True
Power
Level", the level entering the MSA.
* True Power Level = Signal Power - Attenuator setting. Example:
-10.75 - 20 = -30.75
* If the VNA is installed, it is
important to use a power
level of
about
-30 dBm for the first
Calibration Point. The first point is used
as a Phase Reference for the subsequent calibration
points. A very high
input power level may saturate the Log Detector. A very low input
power level will result in very noisy digital
conversion. For
either extreme, the digitized
phase would be very much in error, and,
we would not want to use it as a reference for
the subsequent
calibration points.
* If the VNA is not installed, the
power level of the first Data entry does not matter, even if
the MSA is in saturation.
3.
Configure the Calibration File Manager Window
a. In Graph Window, select Menu, Setup, Initial Cal Manager
b. In Calibration File Manager window,
"Available Files" box, select and highlight Path 1
c. Click "Start Data Entry" box.
d. The "Path Calibration Table" will
display the latest Path 1 Calibration File.
There
are three columns of data with these headings,
ADC
The bit value of the digitized Magnitude value of the Log Detector
dbm
The actual MSA input power to generate the ADC value
Phase
The "Phase Error vs Input Power" Correction Factor, in +/- db
e. The Calibration Boxes will be displayed and
are available for data entry.
Input
(dBm)
box - The True
Power
Level injected into the MSA, in dBm
ADC value
box - The ADC Bit
value, correlated to the True
Power
Level
Phase (degrees)
box - The
phase measurement, correlated to the True
Power
Level
Ref Freq (MHz)
box - The
Frequency at which the calibration is performed.
f. Delete the data,
leaving the Header information.
* The table that is displayed on
initial set-up will have only two rows of data with ADC
values of 0 and the maximum bit count for the AtoD Converter for your
MSA.
* The data shown in the above Path
Calibration Table are approximate values for a
SLIM MSA.
* These are old calibration numbers
that we do not want in a new Path Calibration.
* Move the Mouse cursor
into the displayed Path Calibration Table, Left Click and Highlight
all the
rows of data under the Header information.
* Delete the data, by pressing the
"Delete" key on the keyboard
4.
Calibrate this MSA Path, using multiple steps and True
Input Power levels.
a. Enter into
the "Input (dBm)" box, the True
Power
Level
injected into the
MSA.
* True
Power
Level =
Signal Power -
Attenuator setting
* Example, -10.75 - 20 = -30.75
(type
the value, -30.75, without the suffix, dbm)
b. Click the "Measure" button.
c. Automatic measurement and data entry will
occur:
* The software will test for an error condition
for Center Frequency and Sweep
Width.
* The software will read
the Center Frequency and install it in the "Ref Freq (MHz)" box.
* The
software will read the Magnitude Analog to Digital Converter 10 times,
and average
the Bit values. It will then
enter the average Bit value in the "ADC value" box.
* If VNA is installed, the software will read
the Phase Analog to Digital
Converter 10 times,
convert Bits to Phase,
and average the Phase values. It will then
enter
the Phase value
in the
"Phase (degrees)" box, in degrees.
* The software will not
enter any value into the "Input (dBm)" box. You must manually
enter the True
Power
Level
injected into the MSA (in
dBm). You may do this before or
after clicking the "Measure" button, but certainly
before clicking the "Enter" button.
* Note: You
may make repeated measurements at a Calibration Point without clicking
the "Enter"
button. Simply, re-click the "Measure"
button.
d. Click the "Enter" button to transfer the
box data.
* If this is the first Calibration
Point in the Path Calibration (for this Path),
* A new
box will be created, called Ref Phase (deg). For VNA, this
becomes
the Reference Phase for all
subsequent Calibration Points.
* The Phase values are only used for
VNA
operation. If the VNA is not installed,
the values
will be meaningless. Or, the "Phase" boxes may not even be
shown.
* For all Calibration Points,
* The Input Power and its correlated ADC bit value is entered
into the Path Calibration
Table under the headings "dbm" and
"ADC".
* The
Reference Phase is subtracted from the Measured Phase, and the result
is entered
into the Path Calibration Table under the
heading "Phase". This is the "Phase Error
vs Input Power Correction
Factor. It is used to compensate for the phase error created
for different input power levels to the
VNA. Used only for VNA.
* The
boxes will clear and be ready for the next Calibration Point.
e. Change the attenuator setting for a new
Input Power Level (for the next Calibration Point)
* You
may use higher or lower power; it makes no difference. But it is
important
that no two Calibration Points have the same input
power
level.
f. Return to 4-a. and follow the steps for
each Calibration Point. Basically the steps are:
Apply True
Power
Level, Enter
Input Power,
Measure button, Enter button. Repeat
for all
Calibration points.
* You would like to take
as many Calibration Points as possible. An MSA may have a
dynamic range of 100 dB +/- 20 dB, but
saturation limits
can be as high as 0 dBm and
noise floor inputs as low as as -130 dBm, depending
on the MSA's
topology.
* When calibrating points in the
input level range of 0 dBm to
-35 dBm, attenuation
steps of 2 dB or 3 dB increments is advised.
* When calibrating points in the
input level range of -35 dBm to -75
dBm, attenuation
steps of 5 dB or 10 dB increments is advised.
* When calibrating points in the
input level range of -75 dBm to the noise floor
(approximately -110 dBm), attenuation
steps of 2 dB or 3
dB increments is advised.
You will know you have reached the noise floor when changing the
attenuator will not
change the average Bit count.
5. After the last Calibration Point
is taken, you will manipulate the Path
Calibration Table
a. Click
the "Clean Up" button. This will sort the data points.
b. The first row of data
in the displayed Path Calibration Table, is the lowest input power
Point, taken during Path Calibration.
However, this may not be the ultimate noise floor
of the MSA for this Path.
* Remove the signal
connection from the MSA input connector. Install a 50 ohm load on
the MSA input connector.
* Click the "Measure"
button
* The "ADC value" box will
display the bit value for the ultimate noise floor for this Path.
Take this value and subtract 1% . Highlight
the value in the "ADC value" box and replace
it with the resulting value. Example: If the
displayed value was 4900 (bits), 4900-49 = 4851
* Read the "dbm" column
value of the first row, and subtract 10 (dB). Type this value into
the "Input (dbm)" box. However, if this
value is greater than -120, use the value, -120.0
Examples: If it was -125.33, use -125.33 : If it was -106.88, use -120.0
* Click the "Enter" button, to
install this new data into the Path Calibration Table
* Click
the "Clean Up" button. This will sort the data points.
* Now, the first row will
contain the "ADC" Bit value and "dbm" value of the noise floor.
c. Highlight the "Phase" value of
this
first row.
*
Change this value to the same
"Phase" value, as displayed in the second row. (The Phase
values of
first row and second row will be the same). Highlight the value
in the Table with
the Mouse cursor and type in the new value.
d. Verify the data in the Path Calibration
Table is acceptable, before Saving.
* Click
the "Clean Up" button. This will sort the data points.
* Make
sure all data points are monotonic, that is, an increase in Bit count
shows a resulting
increase of input power.
* Do not allow
any two data points to have the same ADC bit value. If this has
occurred,
delete one of the rows.
* Do not allow
any two data points to have the same "dbm" value. If this has
occurred,
delete one of the rows.
* Click the "Save File"
button. This will replace the MSA Path Calibration File with
the Table that is displayed.
6. The Path Calibration is complete.
a. Exit the Calibration
Manager Window by clicking the "Return to MSA"
button.
b. If
you wish to calibrate another Path,
* Open the Sweep
Parameters window
* Change the
Path number in the "Select Final
Filter Path" box
* Click "OK", "Restart", then "Halt"
* Return to Step
2-c.
and follow the
procedure, replacing any reference to Path 1, to Path X.
F. Frequency
Calibration for
Magnitude:
The frequency, at which the MSA operates, will affect
Magnitude
measurements in both the Spectrum Analyzer Mode and VNA Mode.
This effect is called, "Magnitude Error vs. Frequency". Frequency Calibration will
characterize this effect at multiple frequencies,
and will create a "Frequency
Calibration File". The main MSA software will use this file to
compensate its Magnitude measurements.
Basically, the Frequency
Calibration is accomplished by
injecting a signal of Known Power Level, and of known frequency into
the
MSA input connector. The Magnitude Analog to
Digital Converter is read and converted to "Measured Power" in
dBm. The "Measured Power" is subtracted
from the Known Power Level and the
difference is called the "Magnitude Error vs. Frequency"
Correction Factor. This Correction Factor will be used in the
main MSA software when determining the true input power of the MSA.
The value of Frequency, and the value of "Magnitude Error vs.
Frequency" Correction Factor are both installed
in a "Frequency Calibration Table". The input signal is
changed to another frequency, also at a Known Power Level, and the
measurements are repeated. They are installed in the same Frequency Calibration Table. This process is repeated
for multiple input signal frequencies. The completed Frequency Calibration Table is
then saved as the MSA Frequency Calibration File, and placed into the
MSA Software Folder.
The final accuracy of the
MSA depends on the accuracy of
the Known
Power Level at each frequency, and the number of frequency
calibration
points
taken. The more points taken, the more accurate the
MSA becomes. Of course, we do not
calibrate at "every" frequency. This would require millions of
calibration points. Instead, we calibrate at
several
frequencies and allow the software to interpolate between these
frequencies. Frequency Calibration is
performed
in Path 1, only.
Frequency
Calibration can be either a manual procedure or a semi-automatic
procedure.
* The Basic MSA uses the Manual Frequency
Calibration for the Basic MSA. The MSA will be manually commanded, and each Calibration Point will
be manually entered.
* The MSA/VNA uses the Semi-Automatic Frequency Calibration for the
MSA/VNA.
The MSA
will be swept, and each Calibration Point will
be manually entered.
Note: The following calibration procedures must be performed
before a Frequency Calibration:
Tune coaxial cavity filter
Master Oscillator Calibration
Resolve the Center Frequency of Path 1.
Phase Detector Module Calibration, if the MSA has the VNA installed.
Path 1 Calibration. Other Path Calibrations
are not necessary.
F1. Manual
Frequency
Calibration for the Basic MSA:
The MSA will be manually commanded, and each Calibration Point will
be manually entered. An external, calibrated Signal Source is
used. This
procedure is normally used for the Basic MSA since it has no Tracking
Generator option. But, it can be used for the
full MSA/TG/VNA, if preferred.
Step
by Step Procedure for Manual
Frequency
Calibration:
1. Start with a "Fresh" Frequency Calibration File.
a. Open and Run
the MSA Program (spectrumanalyzer.exe).
b. Halt sweep.
c. In the Graph Window menu, Setup,
select Initial Cal Manager
d. In Calibration File Manager Window's
"Available Files" box, select and highlight (Frequency)
e. The "Frequency Calibration Table" will
display the latest Frequency Calibration File.
*
If this is the initial
Frequency Calibration, the Table will display only two rows of entries,
0.00 MHz and 1000.00 MHz, with a corresponding value
of 0.00 under the
"Error"
column. This is what we want.
* If a previous Frequency
Calibration has been performed, multiple
entries will be
displayed. We want a "fresh table" for a Frequency
Calibration. Therefore, click the
"Display Defaults" button. The Frequency
Calibration Table will be replaced with
the SLIM default Table, showing only the two
rows. Click "Save File".
f. Click the "Return to MSA" button.
2.
Configure the MSA to sweep a Calibration Point.
a. If sweeping, Halt the sweep.
b. Verify that the MSA is
in
the Spectrum
Analyzer Mode
c. If not in SA Mode,
halt the sweep and select it in Graph Window Mode menu.
d. Select the Magnitude Video
Bandwidth Switch to Narrow.
e. Open Magnitude Axis Window
* Enter
0 into the "Top Ref"
box and -100 into the "Bot Ref" box.
* Select Magnitude (dBm) in
"Graph Data" pull-down box.
f. Open Sweep Parameters Window
* Verify
the Select Final
Filter Path box is Path 1. If not, select it.
* In the "Span" box, enter 5 times
the bandwidth of Path 1.
* Enter 100 into the
"Steps/Sweep" box
* Enter 50 into the "Wait" box
* Change the "Cent" box to the
frequency of your first Frequency Calibration Point. This
should be the same frequency that was used for Path
1 Calibration. If you don't know
what it was, use the following
procedure:
* Graph Window menu, Setup, select
Initial Cal Manager
* In Calibration File Manager
Window's
"Available Files" box, select and highlight Path 1
* The Calibration Table for Path
1 will
be
displayed in the Path Calibration Table.
* The top of the Calibration Table
will be, *Calibrated (date) at (xx.xx) MHz.
* The (xx.xx) value is the
frequency,
in MHz, used in Path 1 Calibration
* Click "Return to MSA" button
* Click "OK"
3.
Configure the external, Calibrated Signal Source. There are
several
methods of obtaining a
calibrated Signal Source,
but I will not explain them here. I will only discuss the
requirements of the
calibration
signal, which is injected into the input of the MSA.
a. The
frequency should be adjustable from 100 KHz to 1000 MHz, or
greater. A
narrower
frequency range usable, but the final MSA will be "uncertain"
at any frequency that is
not
within the calibration range.
b. The frequency must be stable to
within 1 KHz.
c. The output power level must be
between -20 dBm and -40 dBm.
d. Whatever
the power level is, it must be known to within .1 dBm (.01 dBm is
preferred).
This power
level will be referred to as "True
Power
Level". The Magnitude Measurement
accuracy
of the MSA is dependent on
the accuracy of this "True
Power Level".
e. Connect the Calibrated Signal Source output to the Input
of the MSA. The coaxial
interconnections should be low loss and as short as possible.
4.
Create a Working Calibration Chart for the Frequencies you will use.
a. Create a Table with these Row and
Column Headings:
Frequency
Measured Power
Level True
Power
Level
Error (T-M)
Point 1
___2______MHz
______________dBm
___________dBm _________dB
Point 2
__________MHz
______________dBm
___________dBm _________dB
Point 3 __________MHz
______________dBm
___________dBm _________dB
etc, to
Point X __________MHz
______________dBm
___________dBm _________dB
b. In the "Frequency" column, fill in the frequency values you
plan to use for each Point.
* Point
1 should be the same frequency that was used for Path 1 Calibration.
* Points 2 through Point X can be at
any frequency that is within the range of the MSA.
Keep in mind that all SLIM MSA's will
operate higher than 1000 MHz. Use Calibration
Points up to the frequency limit
of your MSA.
* We would like to have as
many
Calibration Points as possible. More points taken
will
result in better accuracy of the MSA, but more than
50 points is
probably unnecessary.
I used 20
points for Calibration and obtained good results for the MSA.
c. "Measured Power Level" will be the
power
of the input signal, as measured by the MSA.
d. "True
Power Level"
is the actual input power to the MSA, as provided by
the Calibrated
Signal Source.
* Fill this column with the True
Power Level
at each
Frequency Point to be taken
e. "Error (T-M)" will be the "Magnitude Error vs. Frequency"
Correction
Factor, found by
subtacting
the Measured Power Level from the True
Power Level.
The result can be
a positive or
negative number. Take to two decimal places. i.e., -1.23 dB
5. Command the Calibrated Signal Source and the
MSA for a Calibration Point Sweep
a. Open the Sweep Parameters
Window and change the "Center Frequency" to the same
frequency
as the Calibration Point. Click "OK".
b. Change the Calibrated
Signal Source
Frequency to the same frequency.
c. Click "Restart"
* Magnitude will be measured
at each step in the sweep.
* However, we are only
interested in the measurement at the center of the sweep.
* Verify the peak of the
response curve is in somewhere in the sweep. If it is not in the
center of the sweep, the frequency of the source is not
the same frequency that was
entered as
the Center Frequency for the MSA. This is ok.
d. Allow at least one full
sweep, then Halt.
e. Position the Mouse Cursor over the
center of the response and double Left Click the Mouse.
f. The "L" marker will be displayed,
with the measured Magnitude data in the Marker Box
g. Enter the "L" marker Magnitude
measurement into your Working Calibration Chart, under
the header
"Measured Power Level", for this Frequency Point.
h. Return to Step 5 and
repeat steps a. through g. until you have completed your Working
Calibration
Chart for all Frequency Calibration Points.
6. Open
the Calibration Manager and access the Frequency Calibration
Table
a. In Graph Window menu, Setup,
select Initial Cal Manager
b. In Calibration File Manager Window's
"Available Files" box, select and highlight (Frequency)
c. The "Frequency Calibration Table" will
display the default Frequency Calibration File.
The Table will display only two rows of entries, 0.00 MHz and 1000.00
MHz, with
corresponding values of 0.00 under the "db" column. This is the
"Error" column.
d. Manually enter the new Calibration values
from your Working Calibration Chart into the
Frequency Calibration Table. We will use the "text editor"
process.
* Place the
Mouse Cursor under the "1000.000" row entry, and left click to apply
cursor.
* Enter the
Frequency of Point 1 (in MHz)
* Press the
space bar on your computer to move the cursor to the right
* Enter the Error for Point 1 (in
dB), using correct sign
* Press the "Enter" key on your
computer to move the cursor to a new row
* Enter the Frequency of Point 2
* Press the space bar on your computer to
move the cursor to the right
* Enter the Error for Point 2
* Press the
"Enter" key on your computer
* Repeat this process for all
Calibaration Points, Point 3 through Point X
* They can be entered into the
Frequency Calibration Table in any order
* When finished, click the "Clean Up" button.
This will sort the rows by frequency
7. Save the Frequency Calibration
Table
a. The row containing the default
data at 1000.00 MHz must be changed, or deleted.
* If you
have selected a
Calibration point that is higher in frequency than 1000 MHz,
delete
the default 1000.00 row. Highlight the "1000.00", and its column
values,
and delete them.
* If your highest frequency
Calibration point is lower than 1000 MHz, change the
error value in
the 1000.00 row. Do this by highlighting
the error value in the
1000.00 row,
and replace it with the same value as your highest
Frequency
Calibration Point's eror value.
b. The row containing the default
data at 0.00 MHz may be changed, but must not be deleted.
* It is advisable to make its data
values the same as the values of the next closest
Calibration Point. Highlight its error
value and replace them with the values of the
next closest
Calibration Point.
c. Click
the "Clean Up" button. This will sort the data points.
* Look through the
Frequency Calibration Table and verify that no two rows contain
the same frequency.
d. Click the "Save File"
button. This will replace the MSA Frequency Calibration File
with the displayed Frequency
Calibration Table.
e. The Frequency Calibration is complete.
f. Exit the Calibration
Manager Window by clicking the "Return to MSA"
button.
F2. Semi-Automatic Frequency Calibration for the
MSA/TG
The MSA will be automatically swept, but each Calibration Point will
be manually entered.
Step
by Step Procedure for Semi-Automatic
Frequency
Calibration:
1. Start with a "Fresh" Frequency Calibration File.
a. Open and Run
the MSA Program (spectrumanalyzer.exe).
b. Halt sweep.
c. In the Graph Window menu, Setup,
select Initial Cal Manager
d. In Calibration File Manager Window's
"Available Files" box, select and highlight (Frequency)
e. The "Frequency Calibration Table" will
display the latest Frequency Calibration File.
*
If this is the initial
Frequency Calibration, the Table will display only two rows of entries,
0.00 MHz and 1000.00 MHz, with a corresponding value
of 0.00 under the
"Error"
column. This is what we want.
* If a previous Frequency
Calibration has been performed, multiple
entries will be
displayed. We want a "fresh table" for a Frequency
Calibration. Therefore, click the
"Display Defaults" button. The Frequency
Calibration Table will be replaced with
the SLIM default Table, showing only the two
rows. Click "Save File".
f. Click the "Return to MSA" button.
2.
Configure the MSA and Tracking Generator
a. Open and Run
the MSA Program (spectrumanalyzer.exe).
b. Verify that the MSA is
in
the Spectrum
Analyzer Mode
* If not,
halt the sweep and select it in Graph Window Mode menu.
c. Halt the sweep.
d. Select the Magnitude Video
Bandwidth Switch to Narrow.
e. Open Magnitude Axis Window
* Enter
0 into the "Top Ref"
box and -100 into the "Bot Ref" box.
* Select Magnitude (dBm) in
"Graph Data" pull-down box.
f. Open Sweep Parameters Window
* Verify
the Select Final
Filter Path box is Path 1. If not, select it.
* Enter 1000 into the "Span" box.
* Enter into the
"Steps/Sweep" box, the number of Frequency Calibration Steps you wish
to make. The more Steps, the better the resolution
of the final calibration. I entered the
value, 20. This actually creates 21 Calibration
Steps, since step number 0 is included.
* Enter 200 into the "Wait" box
* Change the "Cent" box to 500 plus
the same frequency that was used for Path 1
Calibration.
Example: if the Path 1 Calibration Frequency was 2 MHz, then enter
the
value "502". If you don't know what it was, use the following
procedure:
* Graph Window menu, Setup, select
Initial Cal Manager
* In Calibration File Manager
Window's
"Available Files" box, select and highlight Path 1
* The Calibration Table for Path
1 will
be
displayed in the Path Calibration Table.
* The top of the Calibration Table
will be, *Calibrated (date) at (xx.xx) MHz.
* The (xx.xx) value is the
frequency,
in MHz, used in Path 1 Calibration
* Click "Return to MSA" button
* Click the "Signal Generator"
button to
change to "Tracking Generator. This will configure
the MSA to use
the Tracking Generator output as the Calibration Source.
* Click "OK"
3.
Configure the Tracking Generator as a Calibrated Signal Source.
a. Requirements of a Calibrated Signal Source, which is injected into the input
of the MSA:
* The
frequency should be adjustable from 100 KHz to 1000 MHz, or
greater.
* The frequency must be stable to
within 1 KHz.
* The power level must be between
-20 dBm and -40 dBm.
* The power level must be
characterized over a frequency range of .1 MHz to 1000 MHz
* That is, whatever
the power level is, it must be a known value to within .1 dBm
(.01 dBm is
preferred). This power level will be referred to as "True Power
Level".
The Magnitude Measurement accuracy of the MSA
is dependent on
the accuracy of
this "True Power Level".
b. The
specifications of the Tracking Generator:
* Frequency range is from 1 KHz to
greater than 1050 MHz.
* Frequency stability to within 3 Hz.
* The
RF output level is approximately -10 dBm, however,
* Level is not uniform across
its entire range of .1 MHz to 1000 MHz (and above),
* Expected ripple is
about 2 dB.
* The
output level of the
Tracking Generator can be characterized (calibrated) over frequency.
There are several methods of characterizing the Tracking Generator, and I
will not explain
them
here. But, if the Tracking Generator is used directly, as the Calibrated Signal Source,
it must
be characterized.
c. If
the
Tracking Generator is used to drive a leveling circuit, such as a
Limiter or Leveler, the
Tracking
Generator does not need to be
characterized. Only the leveling circuit needs to be
characterized. It is considered the Calibrated Signal Source.
d. For either method, connect the Calibrated Signal Source output to an attenuator.
* The
attenuator should attenuate the Signal Source output power to approximately, -30 dBm.
e. Connect the attenuator output to the Input
of the MSA.
* The coaxial
interconnections should be low loss and as short as possible.
4. This step not used.
5.
Critically Sweep, to read the Calibration Points.
a. Click "Restart". Magnitude will be measured
at each step in the sweep.
b.
Verify that the graphed Magnitude response is a horizontal line,
although there may
be a
large amount of ripple. The measured levels should be close to
the True
Power
Level
of
the Signal
Source output, +/- 2 dB.
c. Halt after at least two full
sweeps. The MSA has now recorded
Magnitude data for each
Frequency
Point step
in the sweep.
6.
Calibrate for each Frequency Point of the sweep.
a. In Graph Window menu, Setup,
select Initial Cal Manager
b. In Calibration File Manager window,
"Available Files" box, select and highlight (Frequency)
c. The "Frequency Calibration Table" will
display the default Frequency Calibration File.
* The Table will display only two
rows of entries, 0.00 MHz and 1000.00
MHz, with
corresponding values of 0.00 under the "Error" column.
d. Click "Start Data Entry" box
e. The following Buttons will be displayed
* "Next Point". This will
increment through each of the recorded Magnitude steps
* "Prev Point". This will decrement through
each of the recorded Magnitude steps
* "Enter". This will calculate
and enter this step's Calibration into the Calibration Table.
* "Enter All". This will calculate and enter all
steps into
the Calibration Table.
f. The following Boxes will be displayed
with data already entered.
* "Point
Number" box will display 0. This is the first data Point and
will become the reference.
* "Freq (MHz)" box will display the
Frequency
of this Point
* "Measured Power (dB)" box will
display
the Magnitude reading of this Point in dBm. It
is important that this measured value, in dBm, be
the same as the True Power
Level of
the Calibrated Signal Source injected into the MSA,
within
0.1 dB or better, if possible.
If it is not, the Path 1 Calibration may be in error.
g. Click the "Enter" button, this occurs:
* Software
reads the "Freq (MHz)" box and install its
value into
the Frequency
Calibration Table, under the column, "MHz"
* A new box
appears with the label "True Power (dBm)". It contains
the same
value as the "Measured Power (dB)" box.
This
becomes the Reference value for
subsequent calibration points.
* Software
reads the "Measured Power (dB)" box and
subtracts its
value from the value
in the "True Power (dBm)" box. For
the first Frequency
Calibration Point, the result is
0.00. It
installs this result of 0.00 into the Frequency Calibration
Table,
under the
column, "db", in the same row as the just entered,
Frequency. This is the "Magnitude
Error vs. Frequency" Correction
Factor. It will be used in the main MSA software when
determining the true input power to
the MSA, during normal Magnitude Measurements.
7. Select
the next Frequency
Calibration Point.
a. In the Calibration File Manager
Window, click the "Next Point" button.
* If this is not the correct Frequency
Calibration Point, continue clicking the "Next Point"
button until you
reach the correct Point.
* The "Point Number" box will
increment by 1.
* The "Freq (MHz)" box will display
the frequency of the new Frequency
Calibration Point
* The "Measured Power (dB)" box will
display
the Magnitude reading of the Point, in dBm.
This value will probably not be the True Power Level
on the input of the MSA.
* The "True Power (dBm)" box will
display the True Power of the previous point.
b. Enter the Calibrated Signal Source's True Power
Level at
this Calibration Point into
the "True
Power
(dB)" box.
* Highlight the value in the "True Power (dBm)" box and replace it with the value
of the
Calibrated Signal Source's True Power Level.
c. Click the "Enter" button
* Software
reads the "Freq (MHz)" box and install its
value into
the Frequency
Calibration Table, under the column, "MHz"
* Software
reads the "Measured Power (dB)" box and
subtracts its
value from the value
in the "True Power (dBm)" box. It
installs the result into the Frequency Calibration
Table,
in the same row, under the column, "db". It can be a positive or
negative value.
This is the "Magnitude Error vs. Frequency"
Correction
Factor for this step.
d. Return to 7. and repeat the
step procedures for the next
Frequency Calibration Point.
* Basically, the steps are:
Select each Frequency Point, insert True Power, "Enter" into
Calibration
Table. Repeat
for all Calibration points.
* We would like to have as many
Calibration Points as possible. More points taken will
result in better accuracy for the MSA, but more than
50 points is probably unnecessary.
8. Save the Frequency Calibration
Table
a. The row containing the default
data at 1000.00 MHz must be changed, or deleted.
* If you
have selected a
Calibration point that is higher in frequency than 1000 MHz,
delete
the default 1000.00 row. Highlight the "1000.00", and its column
values,
and delete them.
* If your highest frequency
Calibration point is lower than 1000 MHz, change the
error value in
the 1000.00 row. Do this by highlighting
the error value in the
1000.00 row,
and replace it with the same value as your highest
Frequency
Calibration Point's eror value.
b. The row containing the default
data at 0.00 MHz may be changed, but must not be deleted.
* It is advisable to make its data
values the same as the values of the next closest
Calibration Point. Highlight its error
value and replace them with the values of the
next closest
Calibration Point.
c. Click
the "Clean Up" button. This will sort the data points.
* Look through the
Frequency Calibration Table and verify that no two rows contain
the same frequency.
d. Click the "Save File"
button. This will replace the MSA Frequency Calibration File
with the displayed Frequency
Calibration Table.
e. The Frequency Calibration is complete.
f. Exit the Calibration
Manager Window by clicking the "Return to MSA"
button.
XP Problem
Here is a
strange problem that I had when I first started using my new WinXP Pro
computer and the MSA. After opening and running the MSA software,
the display would graph the correct results for the Spectrum Analyzer
for a few seconds. Then the Magnitude trace would begin to
disappear. I could "Halt" the sweep and click "Restart".
The Graph would be normal for a few more seconds and go away
again. I would repeat this process for about a minute and the MSA
would be normal for the rest of the time I had the MSA session
open. I found this Question and Answer on the internet:
Q: If a logic 1 is
written to the Control Port, bit
0, (Strobe), my PC clears all of the port bits once every five seconds
for about a minute.
> A: Some versions of
Windows XP look for devices
by periodically writing to the port. A registry key can disable this
behavior. You
can make these changes in
Windows' regedit utility.
The following
registry setting disables the port writes:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Parport\Parameters]
"DisableWarmPoll"=dword:00000001
The following registry
setting enables the port
writes:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Parport\Parameters]
"DisableWarmPoll"=dword:00000000
>
This must be for a version of XP which I don't
have. I could not find the "Parameters" file. However, I
did find this:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Parport]
"Start" = 3
I double clicked the "Start", and an Edit window
opened to allowed me to change the value. I changed the value
from 3 to 4. I saw this somewhere else on the internet.
This fixed my problem.
As always, use caution when working with the registry, which contains
critical values for configuring and running the PC.
Windows XP has another feature that previous Windows versions do not
have and should be modified to prevent "weird" displays when
resizing. Perform the following procedure:
You need to disable this as follows
(translated from German interface):
Start => Control Panel => Display and
Design => Display => Appearance => Effects
=> Show Window Content while dragging.
Uncheck this box.
End of Page
You can
email me, Scotty Sprowls, with questions or comments
at: wsprowls@yahoo.com. I'm a retired RF Design
Engineer with plenty of time to answer you. Best Wishes, all!