As mixers need to be operated in saturation mode, I temporarily take the amplifier channel used for IRMC demodulation to amplify the signal from DDS. DDS provides about -6dBm signals. With the mentioned amplifier, LO was amplified to about 5dBm. At the same time, the RF signal was about -15dBm.

When we scan the CCFC phase with a sine wave, the demodulated signals will deviate from sine wave if the demodulation process has problems. So I did this test with 5dBm LO (shown in attached figure 1) for different RF power (-15dBm, -9dBm, -6dBm and -3dBm). These tests are in attached figures 2 to 5. All these figures seem to provide good shape demodulated signals (sinusoidal). From these figures, we could also see that the pk-pk signal also increases with the increase of RF power almost linearly (115mV, 206mV, 288mV, 380mV).

I also checked the CCFC error signals for these cases(figure 6,7,8). They are consistent with the error signals we found in elog2308. And apparently, better SNR is achieved with -3dBm RF power.

(We could add 12dB+12dB+3dB attenuator for the -3dBm signal to simulate a factor of ~25 decreases of CCSB power)