Design of recursive digital filters with variable characteristics

摘要

AbstractA new method for changing the cut‐off frequency of infinite impulse response (IIR) digital filters with a single parameter is derived. the method is based on the use of the Taylor series expansion of the lowpass‐to‐lowpass frequency transformation. the filter structure is a parallel connection of real or complex allpass sections. the tuning range is several octaves for narrowband filters. By taking also the complementary output, a power‐complementary filter pair with tunable crossover frequency is readily obtained. Tunable centre frequency and bandwidth are obtained by incorporating a special lowpass‐to‐bandpass transformation into the structure. Design examples and a description of a signal processor implementation a