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GATE 2021 IN – Question 31

Communication and Optical Instrumentation · Analog and digital communication · 1 mark · Numerical answer

A tone-modulated AM signal has modulation index 0.6. Its power efficiency is ______ % (one decimal place).

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Correct answer: 15.0 to 15.5

Explanation

For conventional AM the useful sideband fraction is η=m²/(2+m²). With m=0.6, η=0.36/2.36=0.152542. In percent rounded to one decimal this is **15.3%**; the remaining power is the carrier.