Box-Section Microstrip Band-Pass Filter with Cross-Coupling

In this paper, a microstrip bandpass filter of box-section structure with cross-coupling is presented. The coupling matrix method is adopted to analyze the response characteristics and a bandpass filter with asymmetric responses based on E-shaped dual-mode resonator is developed. The center frequency is 6.4 GHz, with bandwidth of 0.8 GHz. The minimum insertion loss in passband is 1.9 dB. The transmission zeros in stopband are located at 4.5 GHz and 7.6 GHz. The upper and lower stopband rejections are better than 35 dB and 47dB respectively. The effective overall size is about 0. 34λg*0.43λg. The proposed filter has compact size, high stopband rejection and good selectivity.