PWB-PDM, Phase Detector Board, size-A
Use your mouse's "right click" and "Save Link" to download:
a.  SKPWB-PDM, Schematic, in ExpressPCB software.
b.  PWB-PDM, PWB Artwork, in ExpressPCB software. Use to order from Express.
There is no Parts List.

Description
    The Base PWB-PDM is a printed wiring board that is designed and layed out to create a 360 degree, Phase to Voltage Converter.  The frequency of operation depends on the components, which are not specified with a parts list.  It was originally designed to be used in the MSA/VNA at 10.7 MHz.
  The J1 (Reference) has a low pass filter-diplexer designed into the circuit, but it is optional.  The minimum input to J1 (Reference) or J2 (Input) is -20 dBm.  The maximum inputs are +18 dBm or 5v pp square wave.  Input impedance is 50 ohms.
    The U2 and U3 circuits square up the J1 signal and send it to the input of U4.  U4 can be externally commanded to output the signal normally, or invert it (180 degree phase change).  This signal triggers U5 to change it's output state to "0".
    The J2 (Input) signal is buffered and squared by U6 and U7, then applied to U8.  U8 is a pulse generator that outputs a 10 nsec, negative going pulse.  It is triggered on the positive going, leading edge of it's input.  This U8 output pulse "clears" the U5 state, causing it's output to return to a "1" state.
    The amount of time that U8 is in a "0" state compared to the amount of time it is in a "1" state is the ratio of the phase of the two input signals.  The output of U8 is a combination of square waves with a frequency of twice the input frequency.  But, if the output is integrated with a capacitor, the high frequency component is filtered out.  This leaves a DC voltage that will vary from 0 volts to + 5 volts, depending on the phase difference of the two input signals.  If the voltage is exactly 0 volts or +5 volts, the two signals are in phase (0 degrees or 360 degrees).  When both signals are close to being in phase, U8 has a certain amount of time it can't decide to be in a 1 or 0 state.  This is called the "Zone of Uncertainty", or "Indeterminate Area", or in laymans terms, the "crap zone".  Therefore, voltage outputs that are near 0 volts or +5v are not used.  If the Phase Volts is near this area, U4 is commanded to invert and the U8 output will change to represent a 180 phase differential.  This PDM will be far away from it's "crap zone" when the two signals are separated by at least 15 nsec.  This equates to a phase differential of about 58 degrees at 10.7 MHz.  The DC output voltage at +/- 58 degrees is either +.8 volts or +4.2 volts.  So, any voltage between these two levels represents good phase information.  I suggest using voltage data between +1.0 volts and +4.0 volts.  This will guarantee valid phase information, and an instantaneous dynamic range of 216 degrees.  A minimum dynamic range of 181 degrees is required for operation in the VNA.  The conversion factor for the PDM is 5v/360 degrees, or 13.89 millivolts per degree.
Updated 8-13-07:  Add P2 connector, C19 and FB2.  This puts the phase converter I.C.'s 5 volts on P2-pin2.  This is used only when this SLIM PDM is used in the MSA/VNA configuration.  This voltage supplies the 5v for the SLIM AtoD Converter, and more importantly, the reference voltage for the Phase AtoD conversion.  This will allow a more precise Phase measurement, due to normal voltage fluctuations of 5 volt regulator I.C.'s.


PWB-PDM, artwork for the PDM board
 
    This layout is the artwork for the PDM board.  Do not use as a parts locator for any other SLIM module.

SKPWB-PDM, Schematic of PDM board