Based On Dbr Filter Microstrip Diplexer

With the satellite communication system demands increase and miniaturization of RF circuits and integration requirements, and the performance of microstrip filters and diplexers got much attention. As the filter based on dual behavior resonator(DBR) can independently control attenuation points, with the insertion loss and good stopband attenuation of the advantages, the microstrip filters and diplexers based on DBR has important academic value and prospects. Defected Ground Structure(DGS) can be formed at a certain stop-band frequency range, easy to define the structure of the unit structure. Dual-band Stub (DBS) structure which formed by Spiral Compact Microstrip Resonating Cell (SCMRC) and microstrip lines, provide an easy-to-control dual-stopband. Their size is relatively small due to slow-wave characteristics. This article in the filter and diplexer based on the DBR structure were added to the DGS and DBS structure was studied and made.Firstly, the basic theory and implementation methods of filter and diplexer are described briefly in this article. And then to C-band satellite communications system for the application background, according to the design methods of the filter based on DBR of the open stub,we design the C-band satellite communications microstrip diplexer.Then on the analysis of the relevant parameters of DB-DGS and SP-DGS, we design a quasi-elliptic low pass filter based on the DGS. Join this low-pass filter in microstrip diplexer in order to improve performance. The test results show that the diplexer insertion loss is less than 1.4dB, isolation is better than 64dB.Meanwhile, the analysis of the relevant parameters of the DBS structure, we design a DBS structure and add it to the diplexer. Physical test results show that the receiver filter insertion loss is less than 1dB, the transmitter filter insertion loss is less than 1.3dB, the whole diplexer isolation is better than 62dB to verify the feasibility of the method.Finally, the paper summarizes the work of proposed future research directions.