Studies On Compact Technology Of Microstrip Filter In Wireless Communication System

Microwave filters are critical devices in wireless communication systems, whichare widely used in military and civilian communication systems and mainly used for theseparation of the spectrum information and suppression of signal interference. Due tothe rapid development of wireless communication technology, on the one hand, thecommunication system performance improves continuously, with increasing demandsfor the miniaturization of the system; the development of miniaturization, integration,and wireless communications equipment with high reliability has become an inevitabletrend, which can meet the electrical performance with smaller size. On the other hand,due to the continuous increase of the communication system, the frequency bandresources assigned to every communication system will become more and more narrow;in order to reduce the mutual influence between the signals, high-performancemicrostrip filters are being greatly required.Studies on compact technology of microstrip filter in wireless communicationsystem is carried out in this paper, and the main work is as follows:Firstly, studies on recently published microstrip filters, is carried out to analyze thedesign ideas of each microstrip filter in compact technologies, including classicdumbbell DGS (Defected ground structure) filter, resonant ring DGS filter, fractal filter,DMS (Defected microstrip structure) filter, dumbbell resonator structure filter, coupledline resonator structure filter and hairpin resonator structure filter and so on. And wecould present our own views and improvement measures based on the above analysis,which contributes to propose novel filter structure and achieve better performance offilters by ourselves.Secondly, for the problem of energy leakage of the DGS filters in the bottomground, and greatly requirement of compact and high-performance microstrip lowpassfilters, two novel meandered-slot dumbbell and windmill resonators for designingmicrostrip filters are presented. Both of the microstrip lowpass filters are thesingle-layer circuit structure, without any slits etched on the ground plane. The detaileddesign process of the both filters is presented in this paper. Compared with otherpublished compact and wide stopband microstrip lowpass filters, the two microstriplowpass filters implemented in this article have superior performances in compactnessof the size structure and the stopband rejection width. Finally, the design procedure of how to fast achieve microstrip lowpass filter with compact size and wide stopbandrejection for desired frequency response is summarized.Lastly, the compact technologies of the microstrip filters, including DGS, DMS,fractal structure, resonant ring structure and so on, are introduced in the applications ofthe microstrip antenna. A deformed H-fractal design method is proposed, and thesimulated results of the proposed antenna shows71％size reduction compared with theone without the H-fractal method.