Design of Generalized Comb Filters with Asymmetric Transmission Zeros using Arbitrary Cascaded Triplet and Quadruplet Sections

This paper describes an original method for synthesizing generalized comb filters used in radiomobile base stations; the asymmetric transmission zeros (complex or pure immaginary) typically required in these filters are obtained by cascading triplet and/or quadruplet sections. Triplet sections allow to place asymmetric imaginary zeros, while quadruplets introduce pairs of real or complex (symmetric or asymmetric) zeros; in this way both high selectivity and phase equalization can be otained. Measured results from a test filter designed and built validates the theory presented.