Solving the Approximation Problem for Narrowband Bandpass Filters with Equal-Ripple Passband Response and Arbitrary Phase Response

A practical method is presented for solving the approximation problem for narrowband bandpass filters with equal-ripple passband response and arbitrary phase response. The method determines the element values of the low-pass prototype filter and is based on the use of generalized Chebyshev rational functions with arbitrary choice of transmission zero locations. The use of both real frequency and complex frequency trans- mission zero locations is considered. Results of trial design problems are presented and are related to previous design results to illustrate practical realization and performance limitations.