Question

Calculate the power in a DSB-SC signal, if the modulation is 60% and power of carrier wave is 600W?

(a) 120W

(b) 108W

(c) 111W

(d) 102W

This question was posed to me during an internship interview.

I'd like to ask this question from Amplitude Limiting in section Receivers & Transducers of Analog Communications

Answer 1

Right answer is (b) 108W

For explanation: The total power for DSB is PC (^m^2⁄2) = 600X(^0.6^2⁄2) = 108W.

The total power for DSB-SC = PC (^u^2⁄2). (where Pc = Power of Carrier, u = Modulation Index)  = 600 X ((0.6)^2/2) = 108W.