Coefficient Inaccuracy in Transversal Filtering

In recent years, the transversal filter has emerged as an essential signal-processing structure for a large variety of applications in communication systems. A few of these applications are matched filtering in radar or spread-spectrum systems, equalization in data receivers, echo cancellation for satellite communications, and band-select digital filters. The term "transversal filter" originally referred to the continuous-time tapped delay line structure where an output is formed from a weighted sum of the tap voltages. The same basic function has also been achieved using lumped networks to approximate the delay sections. More recently, transversal filters have been realized with digital circuitry using shift registers and digital multipliers, operating on a sampled and quantized input signal. The most recent development 2301 is the emergence of two new technologies, charge-coupled devices (CCDS) and surface acoustic wave (SAW) devices which allow the realization of discrete-time transversal filters without the need for analog-to-digital conversion. The new technological advances now offer the possibility of realizing transversal filters with hundreds and perhaps even thousands of tapweight stages on a single integrated-circuit chip. These developments suggest that extremely sophisticated signal-processing functions can readily be obtained. Specifically, with a sufficient number of taps, a transversal filter can be designed to approximate virtually any specified frequency response as closely as desired.