I paste below a superhetorodyne based Software Defined Radio Architecture for an Rx channel below.
Suppose the IF signal has a max frequency of 50 MHz and 50 MHz IF BW. In that case, is it possible to just use an ADC of only 50 MSps for sampling process?
According to Nyquist, an ADC should sample at 2X the max frequency of IF. But here, the DDC produces 2× samples once the IQ conversion is completed. So I feel like it fulfills Nyquist criteria before sending IQ samples to the PC/DSP. I.e. After the IQ conversion, the number of samples produced is equal if an ADC of twice the speed were used.
This concept is very clearly proposed in this video (timed to the precise point) https://youtu.be/BK9QkHxeYQI?t=430
I see that this may not be a way of getting around Nyquist but can get away with purchasing a slower ADC by using this method for software defined radio?
I also understand that this way of Super Heterodyne design of a Software Defined Radio hardware can be more difficult and expensive and perhaps also outdated and never used compared to Direct Sampling Method architecture. But I am merely interested in the technicality of this concept.