Contents I. Introduction
Combline filters are widely applied as bandpass filters in modern microwave and millimeter-wave system units due to their compactness, asymmetrical selectivity and ease of integration [1]. The combline bandpass filter is comprised of an array of coupled resonators [2]. The resonators consist of line elements 1 to , which are short-circuited at one end, with a lumped capacitance loaded between the other end of each resonator line element and ground, as described in Fig. 1. With lumped capacitors present, the resonator lines will be less than long at resonance, where is the guided wavelength in the medium of propagation at the center frequency of filter passband. The explicit design equations and methods for combline filters with tapped-line input are presented in Ref. [3].