Odd‐degree selective bandpass digital filters interpolating linear phase and constant group delay

Abstract

SUMMARYA novel simultaneous amplitude and phase approximation method is presented for the construction of non-minimum phase odd-degree transfer functions of distributed (or digital) bandpass filters interpolating linear phase and constant group delay at a set of frequencies in the passband. The passband amplitude characteristic is equiripple interpolating exact transmission at the same set of frequencies. In addition, the stopband amplitude characteristic is maximally flat and the filter selectivity is achieved by introducing a number of transmission zeros distributed arbitrarily between zero and infinite frequencies. The resulting transfer functions are always stable for all the cases considered. Typical characteristics for filters of ninth to 15th degree are graphically presented. The transfer functions presented are also capable of realization as distributed microwave, switched-capacitor, digital or wave-digital filters.