Design And Realization Of Multi-band Filter Based On Step-impedance-resonator

With the rapid development of GSM, WIMAX, WCDMA, WLAN, LTE multi-standard communication systems, as one of the key component of microwave communication system, multi-band microwave filter become a hot research in recent years. Depends on the “high performance, miniaturization” trend of microwave communication system, this thesis has designed a series multi-band filters with compact size and high selectivity bases on Stepped Impedance Resonators(SIRs).Firstly, this thesis analyzes the research status of multi-band filter, and presents the significance and content of work. Further, this thesis introduces the basic theory of filter, and systemly elaborates the theories and methods from low-pass filter prototype to multi-band filter.Secondly, this thesis presents a modified tri-section λ/4 SIR resonator and designs series dual-band bandpass filter based on the proposed resonator. The proposed filter enhances the selectivity by introducing transmission zeros. Besides, by loading an open-end stubs to the proposed SIR, this thesis presents a tri-mode resonator, the tri-band bandpass filter based on the novel tri-mode resonator can generates six transmission zeros near the passband. The proposed filter has compact size and high selectivity.In addition, a closed-loop resonator is proposed in this thesis, and the theoretical analysis test result show that it has the similar resonant characteristic with conventional SIR. On this basis, by embedding the high-frequency resonator in the closed-loop, a dual-band filter is designed for WLAN application. Furthermore, a tri-mode resonator is proposed by loading an open-end stub in the closed loop, and a tri-band filter with compact size and high selectivity is designed.