A dual-wideband bandpass filter based on E- shaped microstrip sir with improved upperstopband performance

Abstract

A novel dual-wideband microstrip bandpass filter (BPF) with improved upper-stopband performance is presented. With the use of some special structures such as E-shaped microstrip Stepped- Impedance Resonator (SIR) and input-output cross-coupling feed structure, this filter can generate five transmission zeros which are beneficial for improving its frequency selectivity and upper-stopband performance. Finally the microstrip dual-wideband BPF has been simulated, fabricated and measured. Measurement results show that the two passbands are centered at 3.7GHz and 5.8GHz with the fractional bandwidth of 31% and 13% respectively. Meanwhile more than 50% relative upper-stopband bandwidth with 20dB rejection has been realized. The simulated and measured results are in good agreement.