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LMX2434 as a phase detector for 2GHz signal

Yuval Izhaki
Prodigy 190 points
Other Parts Discussed in Thread: LMX2434

Dear Sir \ Madam

In my design I need to phase compare 2 high frequency signals (2GHz).

I think of  using  the LMX2434 phase detector part and the divider part as follow  :

the first signal go from the signal source (DDS synthesizer) to FinRF input (pin 15,16 of the LMX) directly.

the second signal gos from the same source trough a variable delay to the FinIF input (pin 3) prescaled & divided down to about 600 MHz

The signal from the IF 18 bit counter feed trough the MUX to Ftest output (pin 10)  ( (pre programmed by the microcontroller)

The signal from the MUX out externally connected to OSCin (pin 8) and feed the phase detector trough the 15 bit R counter 

The phase detector is programed to compare 2 20MHz signal 

The DC voltage from the phase detector output should indicate the phase diffrance between the the 2 signals.

My question is : is this design can work?

Please see attached picture describing the design.6114.Phase detector.pdf

  • 0
    TI__Mastermind 27581 points

    Yuval,

    Good question.   I think that this might work, although I am not very confident about it.  If it does work, there will be some quirks and things to iron out.

    1.   If you divide a signal by N, there are N possible phases.  So initially, I think that you might have an indeterminate phase, but once you program the device, then I think that this will be a constant.  I think that the counter reset might help with this, although I am not sure if the RF and IF PLL counter resets are in the same register.

    2.   I am not sure how high the Ftest/LD pin will run, it seems to me that you could just divide this down to 20 MHz.  Also, on this pin, you might choose the "N/2" option because this gives you a better duty cycle

     

    Regards,

    Dean