Design And Implementation Of Bandpass Filter Based On SIW Structure

With the rapid development of mobile communication technology,the radio frequency industry puts forward higher requirements for all kinds of microwave devices.As an important component of RF transceiver,the performance of microwave filter will directly affect the working state of the whole communication system.The substrate integrated waveguide(SIW)structure has the advantages of both metal waveguide structure and microstrip structure,with the merits of low cost,low radiation,low insertion loss,high quality factor and easy integration,suitable for today's RF communication system.This paper aims at the needs of satellite communication,carries out the research and design of bandpass filter based on SIW structure.The main work is as follows:1.To realize the miniaturization of the filter,the defected ground structure(DGS)is designed.A filter structure based on asymmetric circular complementary split ring resonator(CSRR)is proposed.The proposed asymmetric circular CSRR structure is loaded on the ground plane of SIW resonator as DGS structure,and it is designed as a perturbation element and a harmonic element in single and double passband filters respectively.The structure of the filter is not only compact,but also wide stopband.2.To realize the miniaturization of the filter,the slot structure is designed.The SIW bandpass filters with slot structure and metal stubs are designed.A novel cross slot structure is proposed to adjust the resonance frequency of SIW filter,and two rectangular metal stubs are loaded between two ports to improve the matching.The overall size of the filter is 27mm×13mm,and it has good in-band performance.In addition,a kind of rectangular slot structure and a near “?” type metal branch are proposed to design SIW filter.The rectangular slot structure is used to adjust the resonance frequency,and the near “?” type metal stub is used to improve the out-of-band performance of the lower stopband,and the square complementary split ring resonator is proposed to improve the out of band performance of the upper band.3.To form the transmission zero in the lower stopband,additional source load coupling paths are designed.By introducing a kind of novel parallel coupled microstrip line structure between the source and the load,transmission zeros are generated on both sides of the passband,so that the filter has high selectivity.In addition,in order to realize the miniaturization of the filter,the L-shaped slot line structure and the metal throughhole are respectively introduced into a single SIW square cavity to adjust the resonant frequency,and the corresponding coupling scheme between the two source load ports are designed to generate transmission zeros on both sides of the passband.The size of the final designed filter is almost half smaller than that of the former.All the filters designed in this paper have been fabricated and tested,and the test results are basically consistent with the simulation results,meeting the design index.