Hardware Setup: I'm using a PXIe-5668R VSA to acquire RF signal and stream it to FlexRIO 7976R using P2P streaming. Pre-amp PXIe-5698 is also connected and configured with the VSA in NI MAX software.
Software setup: My code on fpga 7976R is basically multiple channel DDC (4 channels). FPGA gets the IQ data from digitizer, DDC them and sends to host when any channel is assigned and enabled there. The IQs received on host are then processed with 1024-point FFT and graphed in log scale (dBm)
Problem: I generated a signal from VST PXIe-5644 and observed it on RFSA soft front panel, and both transmitter and receiver side peak levels came up same. When I change the reference level on receiving end, signal peak stays there unchanged.
But when I enable the pre-amp using RFSA property node in my code (with reference level below -35 of course), changing the reference level down also changes the peak level as well.
What is the impact of Pre-Amp in this case and how to correct for it? Do I have to cater Downconverter gain somehow?
