Research And Design Of Wideband Antenna

With the continuous development of radio technology,the spectrum resources of wireless communication systems are becoming increasingly scarce.More and more wireless devices require efficient data transmission and communication within a wide frequency band or even ultra-wideband range.Therefore,front-end RF antennas with wideband or even ultra-wideband performances have gradually become one of the hotspots in antenna performances research and design.At the same time,modern wireless technology faces increasingly complex application environments,and antenna design must be optimized according to actual requirements and specifications,so as to give fully play to the system’s performance.Antennas with miniaturized,lightweight characteristics,and good performances are also necessary requirements for research and design.In this paper,two ultra-wideband antennas loaded with dielectric lenses and a low-profile composite spiral antenna are designed to meet the special demands for wideband antennas.Firstly,aiming at the application requirements of wideband and high-gain antennas in medical detection systems,a ring coupled planar spiral antenna loaded with a dielectric lens is designed.The antenna uses a ring coupled planar Archimedean spiral antenna as the radiating body,and with loading a hemispherical dielectric lens on the top and a metal conical reflecting backplane on the bottom to form the beam shape and increase the antenna gain.The fabricated antenna is approximately 87.53mm in height.The measured results show that the antenna has a S₁₁ of less than-10 d B,and the axial ratio less than 3 d B in the 3-12 GHz operation band.What’s more,the 3 d B beamwidth of the antenna is less than 70 degree and the gain can reach more 8 d B,showing good directional radiation characteristics.Secondly,based on similar application scenarios,this paper further designs an ultra-wideband planar sinuous antenna loaded with dielectric lens as an extension of application,and introduces an extended hemispherical dielectric lens and a metal conical reflecting backplane to improve the electrical performance of the antenna.The measured impedance bandwidth of the antenna is 0.86-10.39 GHz with the VSWR less than 2,approaching a wideband ratio of 12:1.Meanwhile,the antenna also has a narrow 3 d B beamwidth and a gain performance greater than 7.20 d B.Finally,for the application of regional environmental detection and direction-finding systems,this article presents a low-profile composite spiral antenna with a loaded frequency selective surface（FSS）absorber.The antenna combines Archimedean spiral and equiangular spiral lines and uses a sinusoidal function to construct the antenna radiating body on the Archimedean spiral arm,and uses the absorbing characteristics of FSS units to construct the antenna’s absorbing cavity to achieve unidirectional radiation.The processed antenna profile height is only 33.70 mm,and the measured results show that the VSWR is less than 2,the axial ratio is less than 3 d B and the gain is greater than4 d B in 2-6 GHz,which indicates that the antenna has stable circular polarization radiation performance.