Research On Multilayer Circuit Based On Substrate Integrated Waveguide

Filter is a kind of microwave device widely used in microwave circuit.In RF circuit system,the signal in a specific frequency band can be effectively filtered.Its function is to obtain or eliminate a specific frequency,which is widely used in global positioning,radar,remote sensing and corresponding electrical and computer engineering.As one of the most important applications of filters,the diplexer is composed of two groups of bandpass filters with different frequencies and is widely used in communication receivers.The research value of the multilayer filter is mainly reflected in the simplified structure and the reduced size.In this paper,based on the theory of duplexers,firstly this paper introduces a kind of double single single-mode cavity based on substrate integrated waveguide duplexer.By taking advantage of the TE mode propagation characteristics in the substrate integrated waveguide,the duplex realizes the filtering function of four-cavity double-mode and double-channel by using the middle metal layer input and feeding mode,and omits the coupling between transmission lines at different layer.The duplex realizes the dual-passband filtering function in a limited space,and the return loss reaches below-20 d B.On this basis,we further study and put forward four-order and dual-mode folded substrate integrated waveguide duplexer,by making use of the folded waveguide propagation characteristics of the first layer of motivation two orthogonal mode transfer to the second floor,complete the two-mode signal transmission.Due to the double bandpass isolation ratio did not achieve the ideal effect,a six-order folded dual-mode double-passband filter is proposed,which uses the propagation characteristics of the folded waveguide to transmit the double-mode signal through the two orthogonal modes excited by the first layer to the second layer through the folded waveguide.On the basis of the fourth-order fold duplexer,this duplexer improves isolation and achieves the ideal effect.In addition,based on the theory of double mode topology,the existence of higher-order modes in the cavity is suppressed by trepanning and slotting the middle metal layer of the double layer filter and a dual-layer substrate integrated waveguide filter with higher-order mode suppression is proposed.The proposed filter was processed into a real object for measurement and verification,and the result showed that the maximum suppression level of the filter was lower than 30 d B,which was in good agreement with the simulation results.The propose filter has the advantages of small size,double frequency band and good performance,and is very suitable for microwave systes.