Study On The Application Of Metamaterials In Microstrip Filters

With the rapid development of the wireless communication systems, microwavefilter which act as the key elements of communication system, are demanded toward tohigh performances and miniaturization. The metamaterials, especially defectedmicrostrip structure (DMS) and composite right/left-handed transmission line(CRLH-TL), provide a conceptual route of implementing high performances andminiaturization for filters. This thesis focuses on the research of high performances andminiaturization of microstrip filters. By taking use of new technologies, such as DMS,CRLH-TL, etc., some kinds of novel filters, such as low-pass filters and band-passfilters, are designed and achieved.Defected microstrip structure(DMS) is one kind of metamaterials, which has manycharacteristics that bandgap and slow wave characteristic and so on．If it is applied inmicrowave plane circuits reasonably, it may greatly improve the performance ofmicrostrip filter．Compared with the conventional DMS, the proposed DMS exhibitslower resonant frequency and wider stopband. From the equivalent circuit model, theDMS are analyzed. Based on the DMS, five kinds of microstrip lowpass filters withhigh selectivity and wide stopband are designed.The measured and simulated results arein good agreement, validating the effectiveness and paacticality of the DMS.Composite right/left-handed transmission line (CRLH-TL) is the form ofrealization of left-handed transmission line. The CRLH transmission line (CRLH-TL)with simultaneously negative permittivity and permeability provides low loss,broadband and special phase response.Its unique characteristies of the double negativecan signifieantly improved the performance of microwave devices.Based on thecomposite right-/left-handed transmission-line(CRLH-TL), a microstrip bandpass filterwith ultra wideband is analyzed and designed. Simulation results show the performanceof filters by CRLH-TL has improved greatly, which suitable for ultra-wideband filterdesign.This paper puts forward the novel DMS structure and CRLH transmission-linewhich is applied for the design of microstrip filter.They can meet the filter requirementson miniaturization and high performance in wireless communication system. And thisfurther proves the utility and practicability of the unit structure and the microstrip filter.