Digital Communications: Fundamentals and Applications, 3rd Edition

3.3 Intersymbol Interference

Figure 3.15a introduces the filtering aspects of a typical digital communication system. There are various filters (and reactive circuit elements, such as inductors and capacitors) throughout the system–in the transmitter, in the receiver, and in the channel. At the transmitter, the information symbols, characterized as impulses or voltage levels, modulate pulses that are then filtered to comply with some bandwidth constraint. For baseband systems, the channel (a cable) has distributed reactances that distort the pulses. Some bandpass systems, such as wireless systems, are characterized by fading channels (see Chapter 14), which behave like undesirable filters manifesting signal distortion. When the receiving filter ...