Study On High Selectivity Substrate Integrated Waveguide Filter

As a very important component,microwave filter is widely used in wireless communication circuits,which can effectively filter out the frequency points of a specific frequency in the circuit or the frequencies beyond the frequency points.With the continuous development of communication technology,it is necessary to divide the spectrum resources more carefully,which puts forward higher requirements for the selection characteristics of filters.Substrate Integrated Waveguide(SIW)has the characteristics of small size,low cost and high power capacity,so the design of high-selectivity bandpass filter based on SIW structure is the key research direction in this thesis.The main contents are as follows:(1)A single-band bandpass filter with two tunable transmission zeros is designed based on quadrate SIW resonator.Three quadrate SIWs are cascaded,so that the first higher-order mode of the larger resonator and the fundamental mode of the smaller resonator are coupled into a passband.At the same time,the affected second-order mode by the introduced of metal hole forming two transmission zeros in high stopband.Adjusting the metal hole's location can change the frequency of the two transmission zeros,which improves the frequency selectivity of filter.(2)Based on the rectangular half-mode SIW resonator,a highly selective three-band pass filter with 9 transmission zeros is designed.Adjusting the width of the rectangular SIW resonator,its internal electric field will change accordingly,forming three new stably distributed modes,which are coupled to form three passbands respectively.Cut the rectangular SIW resonator in the horizontal direction to obtain a rectangular half-mode SIW resonator.The original electric field characteristics are retained but the size is reduced by half,and the miniaturization design of the filter is realized.The introduction of a pair of complementary split ring resonator and source-load coupling structure produces a total of 9 transmission zeros outside the passband,which greatly improves the filter's out-of-band suppression characteristics.(3)Based on a 60° fan-shaped SIW resonator,a highly selective three-band pass filter with 9 transmission zeros is designed.Three 60° sector-shaped SIW resonators are cascaded and a row of metal through holes is loaded in resonator 2,so that the fundamental mode frequency of the resonator is greatly shifted to high frequency to form an additional passband.This method uses only two modes The design of the three-band pass filter is realized.The two pairs of complementary split ring resonators and the source-load coupling structure introduced on the upper surface of the filter produce a total of 9 transmission zeros outside the passband,which greatly improves the selection characteristics of the filter.There are 77 figures,4 tables and 94 references in this thesis.