Study On Filter And Filtering Antenna Based On Substrate Integrated Waveguide

High transmission rate,low delay and large capacity scenarios in 5G put forward higher requirements for the performance of microwave components.For example,more frequency bands,broader bandwidth and higher frequency.However,the increasing number of devices and the improvement of integration lead to the pressure of size and cost.Therefore,the key to satisfy these communication needs is to develop a filter capable of multiband operation and high-quality frequency selection,and to realize the integration of filter and antenna.Based on the advantages of substrate integrated waveguide(SIW)such as small size,easy integration and high power capacity,the design method of bandpass filter(BPF)and filtering antenna are studied in this paper.The main contents are as follows:Firstly,based on isosceles trapezoid full-mode SIW structure,a right trapezoid half-mode substrate integrated waveguide resonator(RTHMSIWR)is proposed for the first time,which further reduces the volume of the cavity.On this basis,a method for single-band and multiband filters design is studied.By controlling the ratio of the upside length to height of RTHMSIWR,the fundamental and higher-order modes are available to generate single-band or multiband response,which provides a flexible choice on band allocation.For verification,a tri-band BPF is designed and fabricated.In order to improve the out-band selectivity,source-load coupling and a pair of complementary split-ring resonators(CSRR)are introduced to produce total seven transmission zeros(TZ).This method not only improves the design freedom of filter,but also maintains the miniaturization of structure.Secondly,a novel 22.5° fan-shaped half-mode substrate integrated waveguide resonator(FSHMSIWR)is proposed firstly by applying the SIW half-mode miniaturization technology to the 45° fan-shaped substrate integrated waveguide resonator(FSSIWR).Its volume is only one sixteenth of the traditional circular SIW.Based on the electric field distributions of fundamental and higher-order modes,another design method for single-band and multiband filters is studied.When feeding on magnetic wall,the fundamental mode is excited to generate passband response,while the higher-order modes can be suppressed.Then a single-band BPF with ultra-wide and deep stopband is realized.When feeding on electric wall,the higher-order modes can be well excited,which provides flexibility to design a tri-band BPF.A pair of CSRR and source-load coupling are introduced to strengthen the out-band rejection of two BPFs.This method can effectively achieve the single-band or multiband response only by adjusting the feeding position.Thirdly,a SIW filtering antenna is designed by integrating the filter and antenna.In order to introduce cross-coupled topology into the design of filtering antenna and improve the out-band selectivity,a compact fourth-order cross-coupled BPF is designed firstly based on the isosceles right triangle SIW resonators.Then,according to the filter synthesis design method,the cross-coupled BPF is improved,and a SIW slot antenna is equivalent to the last resonator of the improved filter to form a filtering antenna.Thus,the bandwidth of the antenna is effectively expanded,and a gain zero(GZ)is generated at high frequency,which improves the radiation efficiency and the maximum gain is 5.98 dBi.