Principles of Communication: Frequency Modulation MCQ

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Frequency ModulationMediumQuestion 20238

Question

The modulation index β in FM is defined as:

A
β = f_m / Δf
B
β = Δf / f_m
Correct
C
β = A_m / A_c
D
β = f_c / f_m

Correct answer

β = Δf / f_m

Explanation

FM modulation index β = Δf / f_m. For wideband FM (β >> 1), bandwidth ≈ 2(Δf + f_m) (Carson's rule: BW ≈ 2(β+1)f_m). Commercial FM: Δf = 75 kHz, f_m,max = 15 kHz → β = 5.

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