Stopband improvement of a dual‐mode ring bandpass filter using DGS

This paper presents the improved stopband of a novel dual‐mode bandpass filter (BPF) using an etched H‐shaped defected ground structure (DGS) at 2 GHz. The wide‐stopband characteristic results from the rejection‐band resonant characteristic of the DGS in the harmonic frequency of the dual‐mode BPF. The proposed BPF is designed and fabricated with the following frequency characteristics: central frequency f0 = 2 GHz, 3‐dB bandwidth of 3%, and wide stopband from 2.5 to 5 GHz at −40 dB. The measured results of the fabricated filter show good agreement with the simulation results.