The RBB filter is bypassed and the input signal is swept from LO to (FADC/decimation/2 i.e., the effective first Nyquist zone).
We noticed that the gain drop by almost 7-8 dB (signal strongest closest to the LO).
Is this to be expected? (some sort of ADC sinc response?)
Putting numbers to the settings:
- CGEN = 200MHz
- FADC = 50MHz
- Decimation = 2^1 (Hence effective sampling rate is 25MSps)
- First Nyquist Zone = 0 to 12.5MHz.
The input signal was swept from f_LO to f_LO + 12.5MHz.
Thank you for looking into this case,