Research Of Coaxial Filter Based On New Processing Technology

Filter is one of the important components in the wireless communication system,its performance will have a great impact on the whole communication system.Miniaturization,light weight,high frequency,low cost and easy integration are the current development trend of filters.The rectangular transmission line processed by micro-coaxial process has the advantages of no dispersion,low loss,ultra-wideband,high power capacity and easy integration,using 3D printing technology,small size and complex structure filter can be realized quickly and cheaply.From the perspective of technological innovation,this thesis studies the application of rectangular micro-coaxial transmission line and 3D printing technology in filter design and processing,including the following contents:(1)The characteristics of the rectangular micro-coaxial transmission line are analyzed,and the structure of the 50? transmission line is determined.On this basis,the bandpass filter is designed,and the frequency response curve is obtained by using the electromagnetic simulation software HFSS to establish the filter model.Firstly,a band-pass filter composed of symmetrical resonators is designed.The center frequency of the filter is 24 GHz,the relative bandwidth of 3d B is6.17%,the insertion loss and return loss of the passband are less than 0.5d B and 27 d B,and the physical size is only 9.6mm×1mm×0.9mm.Meanwhile,according to the theory of 1/4 wavelength short-circuit short transversal,a band-pass filter is proposed.The center frequency of the filter is30 GHz,the relative bandwidth of 3d B is 42.7%,the insertion loss and return loss of the passband are less than 0.5d B and 16 d B,and the physical size is 18.8mm×6.37mm×0.9mm.The influence of filter parameters on the characteristics is studied,and the design methods and steps of such filters are given.(2)Through the previous research on 3D printing technology and the comparison of mainstream 3D printing technology.Firstly,the coupling resonant bandpass filter is fabricated using Polymer Injection Molding(Polyjet)technology.The actual measurement shows that the insertion loss in the passband of the filter is less than 1.7d B and the return loss is better than 9d B.The feasibility of using 3D printing technology to process filter is verified.Secondly,in order to solve the problems of processing technology and thermal deformation of resin materials,the structure design was improved and Stereo Lithography Apparatus(SLA)technology was used to test the capacitance-inductance coupling filter.The insertion loss of the filter in the passband is less than1.4d B,and the return loss is better than 10 d B.(3)Aiming at the non-metallic devices processed by 3D printing,the influence of surface metallization process on the physical test performance was studied.The measured results were compared with the simulation results,and the reasons for the differences were analyzed and the corresponding solutions were proposed.