Wideband bandpass filter using open stub loaded square ring

Abstract

A wideband bandpass filter under multiple resonances of stepped impedance ring resonator is proposed in this letter. The classical even- and odd-mode method is used to analyze the characteristics of the proposed resonator. It is observed that the proposed filter can operate at a wideband. For demonstration, a filter with central frequency at 2 GHz and 3-dB fractional bandwidth (FBW) of 96.7% is designed and fabricated. The experiments have good agreement with simulation.