Communications

The bandwidth equals twice the message bandwidth, B = 2W, since both upper and lower sidebands are transmitted.

The modulation index m = Am/Ac is the ratio of message amplitude to carrier amplitude; keeping 0 < m ≤ 1 (≤100%) avoids overmodulation and envelope distortion.

Sideband power fraction = m²/(2 + m²). At m = 1 this is 1/3, so at most one third of total power carries information.

DSB-SC removes the carrier, so all transmitted power is in the sidebands (more power-efficient), but bandwidth is still 2W. It requires coherent detection.

SSB transmits only one sideband, so its bandwidth equals the message bandwidth W — half that of AM or DSB-SC.

Δf is the peak shift of the carrier frequency from its center. The FM modulation index is β = Δf/fm, the ratio of peak deviation to the message frequency.