Research And Design Of Integrated Substrate Gap Waveguide Filter

The microwave and millimeter filters with high performance are required in the fifth generation(5G)mobile communication systems to achieve high transmission efficiency.Unfortunately,the filters designed by metal waveguide are no longer suitable for highly integrated miniaturized modules and systems;and also the microstrip filters are weak in anti-electromagnetic interference,serious in radiation leakage,thus high transmission loss,and high signal interference are induced that degrade 5G transmission efficiency.However,the substrate integrated waveguide(SIW)filter,in which TE mode is transmitted,is one choice for integration and miniaturization,at the same time,a new type of integrated substrate gap waveguide(ISGW)structure has been proposed in this thesis,which adopts multi-layer substrate integration and self-packaging function is realized by using artificial magnetic conductor structure,a great advantage for designing miniaturized integrated microwave and millimeter wave filters.In this thesis,the ISGW technology and hybrid electromagnetic coupling are combined to fulfil the following works on the research and design of the filter:(1)The band-stop characteristics of the electromagnetic bandgap(EBG)structure are measured and analyzed by the inverted microstrip line method and the HFSS eigenmode dispersion method.By analysis of dielectric thickness,dielectric constant,loss tangent,periodic cell period,metal via diameter and circular metal patch diameter of the dielectric substrate,the optimum design of the EBG bandgap is obtained.The impact of the above parameters with variation is considered for design of the ISGW and subsequent filter design.(2)The LC circuit is used to obtain equivalent EBG structure in(I),and the mechanism of the bandgap variation is explained by the expression of the center frequency and bandwidth of the bandgap.By using the stop-band characteristics of the bandgap structure,two integrated substrate gap waveguides with different dielectric layers and microstrip lines are designed.It is confirmed by experiments that the two waveguides have good transmission characteristics in the K and Ka bands,and self-package is realized in the transmission quasi-TEM mode.(3)The circuit equivalent analysis of the hybrid electromagnetic coupling model is carried out using a J-inverted converter with the opposite characteristics of the K inverted converter.Combined with the filter of hybrid metal via and slot coupling,the effects of metal via and slot on the transmission zero position and passband are analyzed.The eigenmode is used to analyze the variation of the resonant cavity structure and resonant frequency of the loaded metal via.The influence of the position of the metal via and its size on the resonant frequency and excitation mode is obtained.From the equivalent circuit theory,the influence of the equivalent inductance and equivalent capacitance of the slot on the transmission zero position and out-of-band suppression performance is analyzed.(4)Based on the integrated substrate gap waveguide technology and the above study,a wide-band pass filter with dual transmission zero and wide stopband is proposed by means of metal via and inverted,"U" type gap cascading.The return loss of the filter is less than-17 dB,and the insertion loss is less than 1.5 dB.The via coupling makes the center frequency at 18 GHz,and the 3-dB bandwidth is 5.82 GHz,thus the relative l d bandwidth ratio is 32.2%.Hybrid electromagnetic coupling leads to two Transmission zeros(TZ)are at 14 GHz and 22.8 GHz.Use of slot coupling leads to achieve a wide lower stopband from 8 GHz to 14 GHz,and wide upper stopband from 22.8 GHz to 30 GHz,with out-of-band suppression of-30 dB or less;The group delay in the from 15.02 GHz to 20.84GHz is stable and around 0.4-0.5 ns.The filter is designed with a symmetrical,simple,and flexible structure,and lowcost materials,and also has good transmission performance.Finally,the filter is fabricated and tested.The test results are slightly worse in the stopband due to the implementation error and assembly process,but the other performances are basically consistent with the simulation.