suppressedcarrier

Suppressed carrier refers to a class of amplitude modulation schemes in which the carrier component is deliberately removed or significantly reduced during transmission. By eliminating the carrier, these schemes conserve transmitter power and allow efficient use of the allocated bandwidth. The most common variants are double-sideband suppressed-carrier (DSB-SC) and single-sideband suppressed-carrier (SSB-SC). In DSB-SC, both upper and lower sidebands are transmitted with little to no carrier present; in SSB-SC, only one sideband is transmitted, further reducing bandwidth and power.

In operation, the modulated signal is proportional to the product of the baseband message and a carrier, for example s(t) = m(t) cos(ωc t) in the simple DSB-SC form. Because there is no carrier envelope to follow, envelope detection cannot recover the original message. Demodulation therefore requires coherent (synchronous) detection with a locally generated carrier aligned in frequency and phase with the transmitter. This imposes design complexity and sensitivity to carrier and phase errors, as well as to channel-induced distortions.

Applications of suppressed-carrier modulation include long-distance analog voice and data links, where power efficiency is important and the channel supports coherent detection. SSB-SC is widely used in air and sea communications, amateur radio, and some telephone circuits, where bandwidth efficiency is critical. Despite its advantages, suppressed-carrier schemes demand more precise transmitter and receiver synchronization and more linear, stable hardware compared with conventional AM, and they can be more susceptible to phase noise and distortion in non-coherent channels.