Research And Design Of High Directivity Antenna Based On Substrate Integrated Waveguide

With the rapid development of communication technology and increasing demand of communication quality,it is necessary for antenna to have greater ability of directivity to avoid electromagnetic noise.Horn antenna could produce uniform distribution of E-field phase at its aperture by modulating internal structure,which generates a beam with high directivity.However,the size of aperture could not be larger than a reasonable range or the uniform distribution of E-field will be broken because of propagating of the spherical wave.People have designed multiple structure to larger the aperture's size for greater directivity but the process of designing is often complicated.In this paper,a high-directivity H-plane horn antenna with large aperture based on substrate integrated waveguide(SIW)is designed.It focuses on the planar design method by SIW and influence of multiple parameters in designing process.It has designed appropriate feed and transition structure.The whole system will have high directivity,low side lobe level and wide operating band by adjusting parameters of structure.The main work and research results of this paper are as following:(1)This paper proposes a kind of planar Cassegrain antenna based on SIW.This one could produce a narrow beam in H plane and a fan beam in E-plane that makes it have both high directivity and stability.Shaped by metal posts,we could design a planar structure translated from spatial one.After analyzing the relationship between each parameter and radiation characteristic,the proposed one could have greater ability of adjusting interior E-field by its sub-reflector.This paper focuses on relevant parameters of sub-reflector and feed horn in order to choosing appropriate numeric value for the best E-field uniform distribution at its aperture.In addition,this paper also expounds the reason of higher side lobe level from the point of sub-reflector's eccentricity.(2)This paper proposes a kind of offset-feeding planar Cassegrain antenna to avoid the blockage of sub-reflector.By selecting essential parameters of structure and setting in reasonable range,the antenna could have a better E-field distribution at its aperture.This paper focus on relevant parameters of sub-reflector and feed horn impacting on radiation.This offset-feeding reflector antenna introduces metal posts wall to concentrate the beam from feed,that improved the utilization of sub-reflector and radiant efficiency.(3)This paper proposes feeds and transitions structure applying to horn in SIW that satisfies the need of Cassegrain antenna's wide operating band.In design process of feed,coupling patch and slot are adopted to realized wide bandwidth performance.For transition structure,this paper optimizes related parameters,base on gradual changing of relevant dielectric constant,for a better impedance matching between aperture and free space,wider operating band and better front-to-back ratio.