Study On Three Cavities Cascading Technique For Substrate Integrated Waveguide(SIW) Bandpass Filters

With the development of wireless communication technology, frequency spectrum resources become more and more scarce, and the narrowband filter is welcomed by the market. Although the traditional rectangular waveguide transmission have a good performance, and the Q value is very high, but its volume is too large, is not easy to be integrated. At the same time, the price is too high. Microstrip transmission line is one of the widely used. It has the advantages of low cost, small volume and so on, but the loss is too large, and the Q value is low. The transmission line is restricted to consist of the estimable filter. In recent years, a new type of transmission line named SIW(substrate integrated waveguide) is presented by some scholars. The transmission contains the common advantages of two traditional structures, the filter constructed by the SIW is applied to the wireless communication technical requirements.The paper design a dual-mode filter which consists of three cavities based on the SIW.By researching the transmission characteristics of SIW, we compared the similarities and differences between the structure and the traditional rectangular waveguide.using the mothod designing traditional filter to devise to dual-mode filter based on SIW. The paper put a filter of single cavity having a perfect performance at first. Achieve cascaded cavities filter on the basis of that single cavity filter. The performance of the cascaded fliter is improved with a certain degree,and the performance mainly reflected in the relative bandwidth. The paper introduces plane cascade of cavities and out of plane cavities.