Study And Application Of LC And Coaxial Cavity Filter

As one of the most important passive components in communication system, the filter’s development influences the performance of a system greatly. Duplexer is a3-port filter and mainly used as the front end in feed system. In virtue of the duplexer, signals can be received and transmitted at the same time while keeping different signals isolated. Nowadays, electromagnetic environment is getting more and more complex while frequency spectrum is nearly run out, then designers confronted with more stringent demands for filters, in terms of performance, volume and cost. As a result, conventional filters can’t meet these requirements any more. So scholars in this field are exploring new structure and materials to address the case.Firstly, the development process of filter together with target and significance of the study in this thesis are introduced. What’s more, content and innovation points of this paper are given. Then, the theory of filter design and the synthesis of cross-coupling matrix are systematically introduced. Meanwhile, the characteristic of LC resonant and the loading capacitance within coaxial are analyzed, then the work applied transmission zeros of LC on anywhere outside the passband to improve the out-band suppression and miniaturize the cavity filter. In addition, the multiplex network theory is analyzed and applied to duplex design. Last but not least, the LC duplexer of UHF/VHF band and the cavity duplexer of3G are designed and implemented. Finally, the work of this thesis is summarized and prospect of future work is brought forward.Relaying on some auxiliary software tools, LC filter and coaxial cavity filter are studied in this paper and the rapid design process is presented as well. Through the physical design and processing, finally finished the study of LC and coaxial cavity filter.