Analysis And Design Of A Variety Of Resonator Bandpass Filter Based On Microstrip

With the rapid development of modern wireless communication technique, wideband communication system meeting the high data-rate transmission and multi-mode communication system handling of multiple communication formats become hot topics. Wideband and multi-band bandpass filter (BPF) are essential components in radio frequency front end of such wireless communication system. Simultaneously, these filters also require good harmonic suppression characteristics. High performance, low profile and low cost are required for commercial filter application. The multi-mode resonator and plane patched resonator are introduced to design the band-pass and dual-band filters in this thesis.The contents of this thesis are shown as follow:First of all, after the theory on microstrip and dual-port networks is described, the classification and design method on micro-strip filters is introduced.Furthermore, the analyses on resonation characteristic for traditional stepped impedance resonator (SIR) and asymmetric SIR are carried out based on the theory for microstrip filters. A new bandpass filter with compact structure and wide upper stopband is designed based on asymmetric SIR structure. Good agreement between measured and simulated results is observed.Moreover, a new stub-loaded multi-mode resonator is presented. The relationship between the3-dB bandwidth and impedances of different branches is obtained based on the odd-even mode method. A wideband bandpass filer with ultra-wide upper stopband is presented. The measured results agree well with the simulations, indicating the validity of the proposed multi-mode resonator.Lastly, the resonance characteristics of triangle-patch resonator with shorted vertex is investigated and used for practical filter design. At the same time, the input and output structure characteristics are also discussed. The cross slot is etched on the triangle patch to reduce the patch size. Finally, the two-order triangle-patch resonator with shorted vertex is designed operating on both915MHz and2.45GHz. The dual-band filter was proved to be useful by the experiments and simulations.