Study Of Miniaturization Of Microstrip And Coaxial Filters

With the development of semiconductor and micro electronic technology, active devices can be integrated easily in wireless communication system. The passive devices like antennas and filters, with compact sizes and high performance, are essential in the development of modern wireless communication systems. However, due to restrictions of the design methods and performance requirements, they are difficult to design. Filters with good performance and compact size have received increased interest, as the basic elements of system, they can also be used as basic cells to design other devices. Therefore, it is significant to investigate the theory on designing high-performance filters.Based on the analysis of synthesis method and structure for designing compact filters, improved CQ structure is presented. The compact filters used UIR and SIR are designed based on this structure. Then, micostrip duplexer and power divider are designd based on the improved filter cells with SIR. The coaxial cavity duplexer with specific indicators is designed in this artical. The work of this article are as following:Firstly, the miniaturization study of filters at home and abroad is disscussed and summarised in this article.The specific research direction of this article is decided.Secondly, the presentation of basic filter theory is made. The calculation method, the key index of theory and the extraction technology of coupling coefficient are mainly introduced. It is the theoretical support for the following work and strengthen the systemic of this article.Thirdly, the improvement of the miniaturization based on the convertional CQ structure is presented in this artical. The designed filters are implemented with UIR and SIR respectively based on the improved CQ structure. Good out-of-band suppression and wide stopband filtering responses of these filters are realized with the compact size. Then, micostrip duplexer and power divider are designd based on the improved filter cells with SIR.Finally, coaxial cavity filter and duplexer are researched and designed.The design method of the coaxial cavity duplexer with specific indicators is introduced. The related parameters are calculated and the appropriate circuit topology structures are designed. The simulation of schematic circuit and three-dimensional structure model of the duplexers are made respectively. The measured results proved the utility and practicability of the proposed design methods.