Multi-mode Resonator Based Microstrip Multi-band Filter Design

With the rapid development of modern wireless communication, more and more communicationsystems are designed in one equipment. In this case, the demand for multiple-band filters arises.Microstrip multiple-band filters based on multiple-mode resonators are of great importance forminiaturization and integration. This thesis mainly concentrates on designing multiple-band filtersbased on different multiple-mode resonators with novel coupling structures to achieve small size andhigh performance.The main work and contribution in this thesis can be summarized as follow:1. Microwave filter design theory is introduced firstly. Also the resonant characteristics ofcommon multiple-mode resonators (Stub-Loaded Resonator: SLR and Stepped-ImpedanceResonator: SIR) are discussed in detail.2. Novel compact dual-band bandpass filter based on single multiple-mode resonator is designed.The upper stopband is widened due to the source-load coupling structure. Totally five transmissionzeros can be created in this filter, with the whole size only0.13λg×0.11λg. The two passbands can beused for GPS and WLAN application respectively.3. Two triple-mode stub-loaded SIRs are proposed to design a novel dual-wideband filter forWimax and WLAN application. Either of the SIRs can not only separately generate one passbandbut also control the passband performance. Fractional bandwidths reach15.4%and10.2%, andupper-stopband extends up to14.53GHz with an insertion loss larger than24.92dB.4. A triple-band microstrip filter with compact size and high selectivity is presented by usingSLR and quarter-wavelength SIR. Multiple transmission zeros can be created to improve stopbandperformance by using new feeding structure. The proposed filter can be used for RFID、Wimax andWLAN application.5. A compact folded triple-band filter with independently controlled passbands is proposed usingthree sets of dual-mode resonators. One transmission zero can be created between each adjacentpassbands to achieve good isolation. Also wide passbands and good passband performance are gained.6. A dual-band diplexer based on two dual-band filters without matching network is designed forWLAN and Wimax application. Central frequencies of channel one are2.4/5.2GHz, and for channeltwo are2.8/3.6GHz. Since there is no matching network, significant size reduction is achieved.