COMMUNICATIONS THROUGH BANDLIMITED TIME‐INVARIANT LINEAR CHANNELS

This chapter discusses the analysis and simulation of bandlimited time‐invariant linear communication channels. In communication systems, the channel distortion manifests itself in two distinct ways: the transmitted waveform is distorted in such a way that the received symbol energy within the symbol interval is reduced leading to a loss in signal‐to‐noise ratio (SNR); the channel distortion results in dispersion of the symbol energy into adjacent symbols resulting in noise‐like terms referred to as intersymbol interference (ISI). In the chapter, the channels are characterized in the frequency domain in terms of amplitude and phase responses that can be arbitrarily specified. It establishes basic filter concepts to generate real carrier and baseband modulated outputs based on an arbitrary input signal. The chapter characterizes a rect(t/T) input signal and develops the output response for an arbitrarily specified filter. The chapter concludes with computer simulated examples relating the characteristics of the ISI to various channel phase and amplitude characteristics.