A Compact Dual-Band Bandpass Filter with High Band Selectivity using Cross-Coupled Asymmetric Sirs for Wlans

Abstract

In this paper, we have proposed the design of novel compact dual-band bandpass filter (BPF) with high band selectivity by using only two asymmetric stepped impedance resonators (SIRs) with one step discontinuity. By arranging the cross-coupled SIRs, three transmission zeros near the passband edges and a high isolation between two passbands are introduced to improve the band selectivity of the proposed filter. The dual-band frequencies of this BPF is implemented by properly selecting the impedance ratio (R) and physical length ratio of the asymmetric SIRs. The bandwidths and the coupling coefficients of the two passbands (2.4/5.2 GHz) can be designed by adjusting the coupling gap between the resonators. The proposed BPF has a smaller circuit size in comparison with previous works using conventional direct-coupling SIRs. The measured results are in good agreement with the full-wave simulation ones.