ABSTRACT
Digital implementations of filters are preferred over analog realizations for many reasons. Improvements in VLSI technology have enabled digital filters to be used in an increasing number of application domains. There are a variety of methods that can be used to implement digital filters. In this chapter we focus on
the use of traditional VLSI digital logic families such as CMOS, rather than more exotic approaches. The vast majority of implementations encountered in practice make use of traditional technologies because the performance and cost characteristics of these approaches are so favorable. Digital filter implementations can be classified into several categories based on the architectural
approach used: general purpose, special purpose, and programmable logic implementations. The choice of a particular approach should be based upon the flexibility and performance required by a particular application. General-purpose architectures possess a great deal of flexibility, but are somewhat limited in performance, being best suited for relatively low sampling frequencies, usually under 10 MHz. Specialpurpose architectures are capable of much higher performance, with sampling frequencies as high as 1 GHz, but are often only configurable for one application domain. Programmable logic implementations lie somewhere between these extremes, providing both flexibility and reasonably high performance, with sampling rates as high as 200 MHz. Digital filtering implementations have been strongly influenced by evolution of VLSI technology. The
regular computational structures encountered in filters are well suited for VLSI implementation. This regularity often translates into efficient parallelism and pipelining. Further, the small set of computational structures required in digital filtering makes automatic synthesis of special-purpose and programmable logic designs feasible. The design automation of digital filter implementation is relatively simple
compared to the general design synthesis problem. For this reason, digital filters are often the test case for evaluating new device and computer-aided design technologies.
