AM Modulation Index (μ = A_m/A_c = E_m/E_c)

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μ = A_m/A_c = E_m/E_c

What each symbol means

SymbolWhat it stands for
μModulation index (dimensionless); fraction of carrier amplitude used by message envelope
A_c, E_cPeak amplitude of the unmodulated carrier
A_m, E_mPeak amplitude of the modulating (message) signal

When to use this

Sinusoidal message and standard AM where envelope is (1 + μ cos ω_m t). Valid for μ ≤ 1 for distortion-free envelope detection; μ > 1 is over-modulation.