Research On Three-dimensional Frequency Selective Surface Based On Square Waveguide Structure

Frequency Selective Surface(FSS)is an infinitely large planar structure arranged by a periodic structure with a specific shape,which can be regarded as a spatial filter and can realize selective propagation.Driven by the rapid development of wireless communication technology and military and civilian needs,FSS has great research and development prospects.Compared to the traditional 2D-FSS,3-D FSS has one more dimension of design freedom to build more resonances in a finite element structure,and it is easier to achieve high filtering performance by introducing more transmission zeros and transmission poles.Firstly,the background and the research status are introduced by this thesis.Based on the model free space,detailed test procedures and precautions are given.Moreover,based on the square waveguide structure,two types of 3-D FSS are proposed: I-groove resonant unit and dielectric resonant unit,the details are as follows:(1)By using square waveguide walls to load I-shaped slots,two types of 3-D FSS are proposed.A band-pass 3-D FSS with elliptical filtering characteristics is designed by introducing a new resonant mode by etching the I-shaped slots on the square waveguide walls of the parallel plate path.The E-field vector analysis of transmission poles and zeros are provided to understand the operating principle of the proposed FSS.On that basis,a dual-mode resonant unit is constructed by loading metallized vias in parallel plate path to achieve a dual-band 3-D FSS with high selectivity and small passband ratio.Furthermore,the analysis of parameter and the E-field vector analysis of transmission poles and zeros are provided to understand the operating principle of the proposed FSS.At the same time,The HFSS simulation results show that the proposed two types of 3-D FSSs have a relatively stable frequency response under TE and TM polarization at different angles,and with smaller unit sizes.(2)A series of 3-D FSS is proposed by loading a dielectric block resonator in a square waveguide cavity.Firstly,a single-polarized bandpass 3-D FSS with quasi-ellipsoidal filtering characteristics is designed by using a square waveguide cavity to load a single-dipole unit.In order to realize the dual polarization,the dipole patch is rotated and folded to design a high performance 3-D FSS by using waveguide loaded folded cross-shaped patch.The equivalent circuit is modeled based on the ADS software and the working principle is analyzed.In addition,a square waveguide cavity loaded square-ring is used to design a band-pass 3-D FSS,which achieves lots of good performances such as dual polarization,satisfied angular stability,and high frequency selectivity,and small unit cell size.Use parameter analysis and equivalent circuit modeling to deeply understand the working principle of the structure,and perform physical processing tests.In order to achieve the requirements of satellite communication systems for multi-frequency applications,a dual band 3-D FSS with high frequency selection characteristics is designed by using a square waveguide cavity to load dual-loop structure.In addition,the filter characteristics and operating mechanism are investigated through the parameter analysis and equivalent circuit model.Finally,the proposed 3-D FSS can be quickly implemented by a simple assembly approach,which further verified that the proposed structures were feasible.