Discussion
An FM signal with \( \beta = 1 \) has first-order sidebands of amplitude \( J_1 = 0.44 \) relative to the unmodulated carrier. The carrier component is \( J_0 = 0.77 \). The power fraction in the carrier is about
Answer: A
Power goes with the square of amplitude:
\[ J_0^{2} = 0.77^{2} = 0.59 \]
so about 59 per cent remains in the carrier, the rest having moved into the sidebands. 77 per cent is the amplitude ratio quoted as a power. 44 per cent is the first sideband amplitude. And 19 per cent is that amplitude squared, which is one sideband's power fraction. Remembering to square before comparing powers is essential when reading Bessel tables.
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