Design Of Novel Substrate Integrated Waveguide Antennas Based On Coplanar Composite Metasurface Structure

With the rapid development of modern microwave and millimeter wave circuit and antenna technology,its function is becoming more and more complex.Nowadays,some antenna equipment is required to be miniaturized,highly oriented and can be radiated in a wide range of angles.in order to achieve the purpose of easy integration of electromagnetic equipment,long-distance transmission of electromagnetic wave signals and wide signal coverage.The beam scanning antenna has high directivity,and the beam direction can be controlled by mechanical rotation,changing frequency and other conditions,so as to broaden the radiation range of the antenna.The leaky wave antenna has the ability to scan the beam with frequency.The leaky wave antenna loaded with substrate integrated waveguide has the advantages of small size,low profile and high gain,so it has been widely concerned by researchers.However,with the development of communication frequency bands to higher frequency bands such as millimeter waves,the volume of substrate integrated waveguides is getting smaller and smaller,how to achieve high precision drilling,metal injection and PCB surface printing brings higher processing cost.There are some performance degradation problems,such as potential machining error and local irregularity leading to antenna pattern distortion and bandwidth reduction.Most of the existing researches use the optimization of step impedance converter or slot structure to improve the radiation or bandwidth performance of substrate integrated waveguide slot antennas,but the flexible adjustment of bandwidth and radiation cannot be realized.In recent years,the SIW leaky-wave antenna loaded with metasurface uses the classical open complementary resonant ring as the metasurface element to simulate the virtual wall in SIW design,replacing the metallized through hole in traditional SIW to realize the small size substrate integrated waveguide slot antenna with excellent radiation and bandwidth performance in higher frequency bands such as microwave and millimeter wave,and loading metasurface is also an effective way of electromagnetic regulation.In this paper,it is proposed that the coplanar rhombus and hexagon metasurface replace the metallized through hole in the traditional SIW structure,and the performance of the virtual wall is realized.the rhombus metasurface has the advantage of low reflection and the hexagonal hypersurface has the advantage of wide bandwidth.We analyze and propose equivalent circuits of rhombus-shaped and hexagon-shaped meta-surface elements,and verify the virtual electric wall and bandwidth performance of the two metasurface elements through theoretical formula derivation and S-parameter extraction method.Then,according to the performance difference of the two kinds of metasurfaces,SIW transmission lines are constructed to achieve the expected transmission performance of low reflection and wide bandwidth,respectively.Furthermore,in order to achieve high-gain beam scanning of these two kinds of SIW antennas,another trapezoid metasurface is introduced to achieve good leaky wave radiation performance.Finally,on the basis of rhombus and hexagon metasurface based SIW transmission lines and antennas,these two kinds of metasurface structures are introduced twice,and the rhombus and hexagon metasurface structures are arranged in different internal and external order to expand to rhombus-hexagon and hexagon-rhombus metasurface based SIW transmission lines and antennas.According to different metasurface arrangements,the antenna can further obtain better and more flexible reflection coefficient and bandwidth performance.We verify the bandwidths andradiations of four SIW antennas both numerically and experimentally.The maximum gains of the four antennas are 18.1 dBi,17.0 dBi,18.8 dBi and 17.1 dBi,where the corresponding relative bandwidths are 10.74%,19.42%,14.13%and 18.38%.The maximum simulated radiation efficiency and aperture efficiency of the proposed antennas are 91.20%and 61.12%,respectively.Our approach for generating flexible and selectable tuned electromagnetic fields from SIWs is applicable for the development of mm-Wave antennas or sensors on PCB-integrated platforms for highly directive scanning radiation.