This chapter begins with a discussion on need of frequency translation. It discusses how simple multiplication by a high frequency sinusoidal signal translates the message to a new frequency band in the frequency spectrum. A detailed discussion on various types of amplitude modulation schemes along with demodulation principles and circuits are discussed. These includes double side band suppressed carrier (DSB-SC), double side band with carrier (DSB-C) or simple amplitude modulation (AM), single side band (SSB), vestigial side band (VSB), quadrature amplitude modulation (QAM). In each case, mathematical representation of signal is presented along with modultation-demodulation scheme. The simplicity of AM detector is highlighted while note is made on its lower power efficiency. Carrier recovery and synchronization issues are addressed for modulation schemes that require coherent detection. Application in television broadcasting and frequency domain multiplexing is followed by a discussion on radio transmitter and receiver.
