Study On Application Of Substrate Integrated Waveguide Technology In The Microwave Filters

Substrate integrated waveguide(SIW) has the advantages of metal rectangular waveguide, such as high quality factor, high isolation, high power capacity, low insertion loss and low radiation etc. And it also has the advantages which metal rectangular waveguide doesn’t have, such as Small volume, light weight, easy processing, low cost, easy to be integrated with other planar microwave structure and so on. The miniaturization design of wide band bandpass filters using substrate integrated waveguide technology,half mode structure and folding structure has become a hot research topic.In this paper, three bandpass filters are made with the substrate integrated waveguide:a folding half mode wide band bandpass substrate integrated waveguide filter with T shaped defected ground structures,a half mode evanescent mode substrate integrated waveguide bandpass filter,a folding half mode evanescent mode substrate integrated waveguide bandpass filter. The folding half mode wide band bandpass substrate integrated waveguide filter with T shaped defected ground structures’ working frequencies cover 2.13~3.15 GHz with relative bandwidth above 38.6%.The half mode evanescent mode substrate integrated waveguide bandpass filter’s working frequencies cover 1.82~3.72 GHz with relative bandwidth above 68.6%.The folding half mode evanescent mode substrate integrated waveguide bandpass filter’s working frequencies cover 1.95~3.40 GHz with relative bandwidth above 54.2%.The folding half mode wide band bandpass substrate integrated waveguide filter with T shaped defected ground structures is 38.2% shorter than normal wide band bandpass substrate integrated waveguide filters with defected ground structures. The folding half mode evanescent mode substrate integrated waveguide bandpass filter is 50% narrower than normal evanescent mode substrate integrated waveguide bandpass filter. The folding half mode evanescent mode substrate integrated waveguide bandpass filter is 37.6% shorter than normal evanescent mode substrate integrated waveguide bandpass filter. These 3 filter are made and measured, and the results match well with the simulation ones.This paper also analyses the equivalent lumped circuit model of wide band bandpass substrate integrated waveguide filter with I shaped defected ground structures, and calculate the transmission matrix through the equivalent lumped circuit model. After that we test the transmission matrix’s S parameters, and the results match well with the simulation ones. This proves the correctness of the equivalent lumped circuit model. From this model, we can build the method of designing of wide band bandpass substrate integrated waveguide filter with defected ground structures.