DESIGN OF TRIPLE-MODE BANDPASS FILTER USING IMPROVED HEXAGONAL LOOP RESONATOR

Abstract

A novel triple-mode hexagonal bandpass fllter with capacitive loading stubs is introduced in this article. The technique, adding an open capacitive stub, is applied to enlarge the equivalent self- capacitance of the resonator, which declines its resonant frequencies. Three radial-line stubs in the center of top layer are used to implement this technique. One mode resonant frequency is varied with the radii of three radial-line stubs, while the other two modes are nearly not afiected. This fllter has a pair of transmission zeros which are close to the passband, thus it behaves with high selectivity. For method validation, a bandpass fllter operating at 2.4GHz is fabricated and measured. The experimental results are demonstrated and discussed.