problem with coherence implemantation

[ramsay]

I have some problem with coherence
implemantation.

We have PXIe- 5663 receiver and PXIe-5673
signal generator.

The question is:

Is possibile to  share commone LO signals, for  phase syncronized and phase coherency in transmiter-receiver
hardware setup?

I had obtained negative results of two experiments :

first case – when RFsignal generator PXI-5652 was associated (in MAX) with PXIe-5450 I/Q signal Genarator and PXIe-5611 Vector Modulator and transmiter should to give
out LO signal by LO OUT connector  in  PXIe-5611Vector Modulator to LO IN connector in front panel of PXIe-5601
Downconverter ,and second case: when RFsignal generator PXI-5652 was associated
(in MAX) with PXI-5601 Downconverter and PXI-5652 Digitizer, and LO signal was
taken from LO OUT connector in  PXI-5601 Downconverter and was given
to LO IN connector in PXIe-5611 Vector Modulator.

I was generate Simple RF pulse by one VI, and was receive this Signal by Rother VI
with triggering function using.

Thanks!

[ramsay]

In both cases all properties connected with LO Signal Transfer  in property nodes of NI-RFSG (In first VI) and
NI-NFSA (in second VI), was activated and right adjusted In Block Diagrams of  both VIs.

[Andy_Hinde · Accepted solution]

Hello ramsey,

The architectures of the PXIe-5673 and PXIe-5663 are different. The PXIe-5663 is IF based, whereas the PXIe-5673 is not. What this means is that when the 5663 and 5673 are tuned to the same center frequency, the LO signals used for each will be at different frequencies.

The 5663 typically uses an IF frequency of 187.5 MHz (sometimes 53 MHz - see the  NI RF Vector Signal Analyzer Help for more info) so whena center frequency of 1 GHz is requeste, the LO frequency will actually be 1187.5 MHz (high-side injection). Above center frequencies of 3 GHz, the 5663 switches to low-side injection so the LO frequency will then actually be 187.5 MHz lower than the requested center frequency.

For the PXIe-5673, since it is direct IQ to RF upconversion, the LO frequency will be the same as the requested center frequency.

So in summary you cannot share the same LO signal for the PXIe-5663 and PXIe-5673. You can however lock them to the same 10 MHz reference clock which will cause the LOs generated to be coherent, but with non-correlated phase noise.

Regards,

Andy Hinde

National Instruments