Digital Modulation and Power Spectrum

Abstract

Modulation is the process whereby message information is embedded into a radio frequency carrier. Such information can be transmitted in either the amplitude, frequency, or phase of the carrier, or a combination thereof. This chapter begins with the basis of mathematical representation of digitally modulated signals. This is followed by a discussion of Nyquist pulse shaping, which is essentially for spectral control. Later, the chapter considers a large number of digital modulation schemes that are commonly used in wireless communication systems, including quadrature amplitude modulation, phase shift keying techniques, orthogonal modulation and variants, orthogonal frequency division multiplexing, and continuous phase modulation. The chapter concludes with a thorough treatment of the power spectrum of the various digitally modulated waveforms considered in the chapter.