Research On Wide Stop Band And Double Pass Band Balanced Filter Based On Substrate Integrated Waveguide

In recent years,based on substrate integrated waveguide technology balanced filters because of its good environmental noise suppression ability of high power and low loss characteristics have been widely concerned and researched,and made a series of technical progress,but the problem of spurious band interference and multi-band can be controllable still have not been resolved.According to the SIW harmonic balanced filter structure by high-order mode caused by passband suppression and dual band flexible design problems in-depth research,design and implementation of the two models with wide stopband SIW balanced filter,designed and produced a two center frequency and band width are flexible and controllable SIW dual-band balanced filter.The specific contents are as follows:1.A single band and a dual-band SIW balanced filter with wide stopband are designed and realized.The harmonic suppression principle,feeding and coupling window optimization design method based on design a single-band balanced filter to achieve wide stopband,out of band rejection in more than 20dB in the range of 2.54f0,where f0 is the design of the center frequency of the passband;then dual-band filter based on advanced balanced topology.The design of dual band balanced filter with wide stopband,using the dual-layer technology,realizes the dual-band design,realization of band suppression in more than 20dB in the range of 2.17 f1,where f1 is center frequency of the first passband design in balanced filter.2.Two SIW dual-band balanced filter with flexible controllable center frequency and bandwidth is designed and implemented.Firstly,the influence of resonant cavity size on the resonant frequencies of the fundamental mode(TE101 mode)and high-order mode is analyzed.The range of frequency ratio that the TE101 mode and TE201 mode in the resonant cavity can construct the first and second passbands is introduced.The influence of the coupling window between the port and the resonator on the two passbands introduces a flexible and controllable design method for the double passband.In order to verify the validity of the theoretical method for designing SIW dual-band balanced filters,a planar second-order dual-band balanced filter was designed.The passband frequency ratio is 1.42 and the bandwidth ratio is 1.07.Verify the effectiveness of the design scheme.For the disadvantages of isolation between the passbands of the planar structure balanced filter and the lack of out-of-band rejection,a quad-order dual-band balanced filter with a stacked structure is designed.Compared with the planar structure filter,the size area is basically unchanged,but the isolation between differential mode passbands and the out-of-band rejection level are effectively improved.For the problem of insufficient common mode suppression,the slotlines are etched on the metal surface of the resonator,which effectively improves the common-mode rejection of the balanced filter.