Research On Dielectric Loaded Horn Antenna

Horn antennas have the advantages of wide frequency band,high gain and stable phase center.It has important applications in the fields of electromagnetic compatibility test,UWB radar detection and reflector antenna feed.However,wider frequency band,higher gain,circular polarization characteristics and the identical 3-d B beam width of E-plane and H-plane are required for horn antennas in many application environments,which puts forward high requirements for the innovative design of the horn antenna.Aiming at these requirements,this paper studies the technology of loading dielectric lens into horn antenna to improve its performances.The main research contents of this paper are as follows:Firstly,high gain double ridge horn antennas（Double Ridge Horn Antenna,DRHA）loaded with dielectric lenses is studied.According to the working principle of DRHA,the bandwidth broadening and miniaturization technology are studied,and a DRHA operated in 1-18 GHz is designed.It is found that the DRHA antenna suffers the problems of large interface phase error and pattern splitting in high-frequency.To solve these problems,two all-dielectric lenses（"Moon"lens and cone lens）are designed and loaded on the designed DRHA respectively,so as to improve the phase distribution of the antenna aperture,suppress the pattern splitting in high-frequency and improve the gain.Simulation results show that the patterns in the 1-18 GHz are improved by the"Moon"lens,and the gain enhenced by up to 6.5 d B.The gain in the 1-18 GHz is 7.5-20.5 d Bi.The results also show that the gain of DRHA loaded with cone lens increases by 1-7 d B in the 1-18 GHz,the3-d B beam width in the 8-18 GHz is about 20^o which is stable,and the pattern is also stable in the working band.The two all-dielectric lenses can be fabricated with 3D printing technology,which has the advantages of simple processing and low cost.Secondly,X-band circularly polarized horn antenna loaded with a dielectric polarizer is designed.First,a dielectric polarizer which can realize linear-circular polarization conversion is designed.Then,a coaxial to waveguide horn antenna working in X-band is designed.The all-dielectric polarizer is loaded on the front end of the linearly polarized horn antenna.The measured S₁₁ of the antenna in X-band（8-12 GHz）is less than-10 d B.It is found that the all dielectric polarizer can convert linear polarization wave into circular polarization wave,and the measured axial ratio（AR）of the antenna is less than 3 d B in X-band.In addition,the measured gain of the antenna increases about 2 d B by the all-dielectric polarizer,and it is is 14.3-15.8 d Bic in the working frequency band.The simulation results of the antenna are consistent with the measurement results,which confirms the broadband,circular polarization and high gain characteristics of the horn antenna.The all dielectric polarizer is also fabricated with 3D printing technology.Finally,the influence of loading dielectric rods on the horn antennas’radiation characteristics is studied.The dielectric rod is composed of two trapezoidal dielectric columns with different sizes（ε_r=2.7）.It is found that the dielectric rod can improve the gain of linearly polarized horn antenna（the gain is increased by 1.71-4.18 d B）in the X-band,reduce the sidelobe（the sidelobe is reduced by 15 d B at 10 GHz）,and realize the same3-d B beam width of the E-plane and H-plane patterns.Due to the equal width beam and low sidelobe characteristics of the dielectric rod loaded horn antenna,it can be used as a source of the reflector antenna.The dielectric rod can also be fabricated with 3D printing technology.