Sideband
In radio communications, a
sideband is a band of frequencies higher than or lower than the carrier frequency, containing power as a result of the modulation process. The sidebands consist of all the Fourier components of the modulated signal except the carrier. All forms of modulation produce sidebands. Amplitude modulation of a carrier wave normally results in two mirror-image sidebands. The signal components above the carrier frequency constitute the
upper sideband (
USB), and those below the carrier frequency constitute the
lower sideband (
LSB). In conventional AM transmission, the carrier and both sidebands are present, sometimes called
double sideband amplitude modulation (
DSB-AM). In some forms of AM, the carrier may be removed, producing
double sideband with suppressed carrier (
DSB-SC). An example is the stereophonic difference (L-R) information transmitted in stereo FM broadcasting on a 38 kHz subcarrier.