GATE 2021 EC – Question 32
Consider a carrier signal which is amplitude modulated by a single-tone sinusoidal message signal with a modulation index of 50%. If the carrier and one of the sidebands are suppressed in the modulated signal, the percentage of power saved (rounded off to one decimal place) is ________.
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Correct answer: 93.93 to 94.87
Explanation
Total AM power is $P_c\left(1+\frac{\mu^2}{2}\right)=1.125P_c$ for $\mu=0.5$, and each sideband carries $\frac{\mu^2}{4}P_c=0.0625P_c$. If the carrier and one sideband are suppressed, only $0.0625P_c$ is transmitted, which is $\frac{0.0625}{1.125}=5.56\%$ of the total, so the power saved is $100-5.56=94.4\%$.