High‐selective triple‐mode bandpass filter using a new capacitive‐loaded patch resonator

Abstract

This Letter proposes a novel high-selective triple-mode bandpass filter based on a patch resonator. The new triple-mode patch resonator is realised by the traditional dual-mode square patch with a floating capacitive-loaded metal patch. The resonance of one higher-order mode can be independently shifted to that of two fundamental modes to form a passband. Based on the proposed filter, three finite-transmission zeros can be produced, and two of them can be controlled well. For the demonstration, a triple-mode patch filter with the centre frequency of 3.5 GHz was designed, fabricated and measured.