Balanced Bandpass Filter Based on Square Patch Resonators

Abstract

This paper proposes a novel balanced bandpass filter that consists of square patch resonators with rectangular slots. The behaviour of the square patch resonator is analysed in detail and its ability for application in balanced filters is discussed. A bandpass balanced filter operating at 1.8 GHz has been designed. The filter is characterized by a simple design procedure, excellent passband performance, and common-mode rejection below 30 dB in the passband.