Question

1. In the demodulation DSB-SC AM signals, there is a need for a phase-coherent or synchronous demodulator for recovering the message signal from the received signal. That is, the phase of the locally generated sinusoid should ideally be equal to the phase of the received carrier. What are the ways by which a sinusiod at the receiver can be generated phase-locked to the phase of incoming carrier signal ? Explain with the aid of block diagrams, and discuss their advantages and disadvantages.

Answer 1

De Demodulation sly using Envelope SDSB-SC AC = m(t) Copwet cit)= Accos (Wett&) Y = SDSB SC X c'(t) = m(t). At coswet & Aclos (Wet+) of DSB-sc Envelope Colt) Detector 1 = m(t). Ach loset x cos( Wet +O) COU A COB = ['cos ch+B) + 401(A-1)] Ac? mit) [ cosun fet + cost cosa Ac?mit) cos un fet 2 Ac ²mlt) + 2 2 1st term 2nd teum . Envelope Detector is same like Low pass filter and here and team has higher frequency component . so it will be blocked and only Ist term will pass Colta 4² met). cosa. Now $=0 Amit) 2 Colta 2 Advantage efficiency is is n = 100% can be used for long distance Communication Disadvantage Demodulation is very complex → It requires high transmission bandwidth