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

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.