Continuous Filter Mathematical Concepts. Volume II. Design of Continuous, Lumped Parameter Linear Filters

摘要

Most filters used in the separation of signals on the basis of frequency are derived by transformation of standard lowpass filter functions. These standard functions include the Butterworth, Chebyshev, Bessel Polynomial, and Elliptic Function filters. The first two and the last of these approximate the magnitude of an ideal lowpass filter. The Bessel Polynomial filter approximates the linear phase of an ideal lowpass filter. All of these prototype filters are discussed herein. To make a practical filter, one converts a lowpass prototype to a lowpass, highpass, bandpass, or bandreject filter. This final filter must have practical element values for fabrication with electronic circuit components. Problems of frequency transformation and frequency and magnitude scaling to give practical filters are discussed. Both the use of passive filters as interstage coupling networks and the design of active filters are presented. (Author)