The Design Of Microstrip Filter Beaed On Half Waveleng Resonator

The rapid development and wide application of wireless communication technology, especially WCDMA、WLATN、WIMAX and UWB, have spurred a tremendous development in communication system. Microwave filter is one of the most important components in wireless communication system, while the communication system requires that the filter should have a compact size, good bandpass selectivity and low production cost. Microstrip filter based on half-wavelength resonator have attracted extensive mention and focus all over the world because of its compact size, good bandpass selectivity and low production cost. In this paper, two novel bandpass filters based on hale wavelength resonator are proposed and studied, in which one is designed to suppress the harmonic frequencies and the other one is for dual-band communication system. These two bandpass filters have been fabricated and measured. The experimental results are found to be in good agreement with the simulated results.The main work in this paper is summarized as followings:1. First a brief introduction about the bandpass filter at home and abroad is given, including the development history、research background、 newest research results and common research method and tool of microwave technology.2. The technical parameters of the microwave filters are briefly introduced. The design principles of the filters arc studied in details, including several important simplified transmission function, the frequency and impedance mapping of the lowpass prototype filter, the microwave implementations of the distributed elements and the equivalent circuits of transmission line resonators. The structures, design principles and performances of the microstrip filters are analyzed and summarized 3. Equivalent circuit、coupling conditions and coupling matrix of the conventional half wavelength resonate filter are analyzed. Taking the advantage of the good bandpass selectivity, combined with shunt open stubs, a novel and compact dual-band banpass filter is presented and the transmission zeros are analyzed. The filter is fabricated and measured, and the simulated results are confirmed by experiment. The feasibility and practicability of this method are approved on the basis of comparing and analyzing the simulated and measured results.4. The wiggly-line structure used in suppression of harmonic frequencies of microstrip coupling lines is pre-studied. A novel filter tanking advantage of rectangular grooves and perturbation stubs are presented. A brief summarization of the simulated result is presented and the measured result match really well the simulated result.