Question: The BPSK signal expressed by Eq. is to be demodulated. As studied in the previous problem, we must multiply an cos ωct by an LO waveform. Now suppose the LO waveform generated in a receiver has a slight "frequency offset" with respect to the incoming carrier. That is, we in fact multiply an cos ωct by cos(ωc + ?ω)t. Prove that the signal constellation rotates with time at a rate of ?ω.
xPSK(t) = ancosωct an = ±1