| With the rapid development of wireless communication system, the communication frequency spectrum resource has become more and more lacking. The performance of filters can directly affect the quality of the system. Now, Microwave cavity filters are widely used in microwave communication, navigation, telecontrol, and satellite communications. And that leads to more and more stringent requirement for microwave cavity filters. Filter with smaller insertion loss, wide band, high power handling, good spurious performance and high selectivity is becoming customers'favorite. At the same time, size, cost and design speed are also the requirement of the clients. Many communication systems use one common antenna for receiving and sending the signal, so there is growing need for the research on diplexer and multiplexer. And that makes filter designers put more energy on the development of microwave filters and diplexers.This thesis mainly explains how to design the iris waveguide filter, diplexer and cross-coupling filter and the theory of them.1. Starting form filter design theory, some kinds of filters and their advantages and disadvantages are presented.2. The design method of the iris waveguide filter and diplexer was detailedly introduced. Common port design is the keystone of the implementation of diplexer and multiplexer. This thesis shows a T-junction with compensating iris. And based on that, X-band diplexer was successfully produced.3. The principle and arithmetic of the cross-coupling technology was analyzed and deduced. From the initial requirement, the transmission and reflection polynomials were established. Then starting from the initial coupling matrix, the final matrix was got by using the matrix reduction. Matlab procedure is used to implement all the steps.4. By using the matlab procedure together with EM software HFSS, the coaxial cavity filter with cross coupling was successfully tuned and that gave full support to the accuracy of the design theory, method and Matlab procedure. |
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