ABSTRACT
Analog modulation (AM) techniques are widely used in broadcasting and for point-to-point radio links. AM broadcast stations use AM, television broadcasting uses vestigial sideband modulation (VSB), stereo radio broadcasts employ double sideband suppressed carrier AM of a sub-carrier to carry stereo information, and HF radio links use single sideband AM. Frequency modulation (FM) is widely used for high-quality sound broadcasting, using large deviation ratios and wide bandwidth signals. Narrow bandwidth small deviation FM is used in cellular telephones which employ analog modulation (AMPS), and also for handheld radios used for voice communications. FM is widely used for high-quality audio broadcasting, for analog cellular telephony, and for analog satellite television transmission. FM offers better interference and impulsive noise rejection than AM, and also the possibility that the S/N ratio at the output of a demodulator can be substantially higher than the C/N at the demodulator input. Wideband FM is also used for distribution of television signals via geostationary satellites.
