ABSTRACT
A variety of modulation schemes are employed in digital communication systems. This chapter presents a variety of modulation schemes along with their power spectra. The power density spectrum of Gaussian minimum shift keying is quite difficult to obtain, but can be computed by using published methods. Analog modulation schemes include amplitude modulation (AM) and frequency modulation (FM). Analog modulation schemes are still used today for broadcasting AM/FM radio, but all other communication and broadcast systems use digital modulation. Digital modulation schemes transmit information using a finite set of waveforms and have a number of advantages over their analog counterparts. Modulation schemes can be designed to provide power and/or bandwidth efficient communication. Continuous phase modulation (CPM) refers to a broad class of FM techniques where the carrier phase varies in a continuous manner. CPM schemes are attractive because they have constant envelope and excellent spectral characteristics.
