Compact fourth and eighth order bandpass filters using quadruple-mode resonators

This paper presents the design and implementation of higher order bandpass filters using the published compact quadruple mode resonator. The resonator is further analyzed using odd and even mode analysis along the symmetrical plane of the resonator. The current distributions of the four resonant modes are given for the analysis of the two even mode and the two odd mode frequencies. Approximate expressions can be derived to predict these resonances using ABCD matrix. For the 4-pole and 8-pole filters, standard Chebyshev lowpass prototype design formulae are adopted to compute the required filter design parameters. The simulated and experimental results are in good agreement.