SIR Double / Tee-band Filter Research And Design

With the rapid improvement of wireless communication technology and the proposed wireless communication treaty (GSM, DCS, WLAN, WIMAX etc.), wireless communication terminals need features such as multi-band performance characteristic, small size, light-weight etc, then the dual-band filter and multi-band filters were proposed. As an indispensable component of communication system, to realize dual-band and multi-band filters with miniaturization and high performance is more challenging.This paper did research on planer dual-band and triple-band filters in communication frequency band. Stepped impedance resonator was used as the filters basic resonance unit and the parallel-couple line was used the feed structure to realize dual-band and triple-band filters. The resonant frequencies of the proposed filters are flexibly controlled, and the whole size is small.Based on dual-section SIR parallel resonance condition, three kinds of dual-band filters were proposed by using X^/2dual-section SIR in this paper. The first one was a simple pseudo-interdigital structure SIR filter; the second one loaded an open stub; the third one loaded two open stubs. To validate the design and analysis, the third one was fabricated and measured. The simulated and measured filters were centered at2.45GHz/5.2GHz and2.41GHz/5.14GHz with3dB bandwidth of6.45%/8%and5%/6.4%, respectively. The minimum insertion loss of the simulated and the measured one were0.61dB/0.8dB and2.1dB/1.79dB, respectively. The whole size was14.87mm*23mm.Based on tri-section SIR parallel resonance condition, this paper presented two kinds of triple-band filters by using tri-section SIR. The first one was a simple pseudo-interdigital SIR triple-band filter. To reduce the circuit size, the second one which used meandering triple-section Xg/2SIR as the basic resonance unit was fabricated and measured. The simulated and measured filters were centered at1.9GHz/3.5GHz/5.2GHz and1.9GHz/3.52GHz/5.23GH with3dB bandwidth of4.7%/10.7%/9.2%and6.3%/8.5%/5.7%, respectively. The minimum insertion loss of the simulated and the measured one were0.46dB/0.46dB/0.56dB and1.28dB/1.75dB/3dB, respectively. The whole size was14.8mm*32.7mm.