Center Frequency Mismatch between NI 5663E Master and Slave

Updated Oct 1, 2019

Reported In

Hardware

  • PXIe-5663E

Driver

  • NI-RFSA

Issue Details

I set up the NI 5663E master and the slave according to Figure 9 of this document. I measured the same RF IN with the master and the slave using the RFSA soft front panel(SFP). Then, I noticed there was a difference in measured center frequency between the master and the slave. Is there something wrong with my NI 5663E? Should I calibrate the device?

Solution

The difference of center frequency is due to the difference of the reference clock. Because onboard clock is selected as the reference clock by default on the RFSA SFP, the 10MHz clock on the NI 5652 is used as ref clock for the master, and on the other hand, the 10MHz clock on the NI 5622 is used for the slave. The difference of center frequency is due to mismatch of the onboard clocks.

To avoid this mismatch, you have two options.
1. Using a splitter, split the signal from REF OUT 2 of NI 5652, and connect the signal to two NI 5622 CLK INs of the master and the slave. Also, change the ref clock sources for both the master and the slave through RFSA SFP>>Device/System>>Freq Ref Src>>CLK IN.
RFSA SFP does not have a way for the master NI 5622 to output CLK OUT, so you have to follow the above set up.
2. Use RFSA Synchronization (TCLk, Shared LO and Reference Clock) example VI, which is designed to use NI5663E as a MIMO system.