| Circularly polarized antenna can improve the quality of signal receiving and transmitting,reduce the requirement of space position.So,it is widely used in communication,imaging and radar systems.In terahertz system,due to the requirement and limitation of working frequency and structure,the antenna in the system should be able to achieve both circular polarization and wideband high-gain radiation performance.In the present research,some circularly polarized antennas have been proposed and proved to be suitable for terahertz systems.However,some of the proposed circularly polarized antennas have complex structures which are not conducive to machining,and some of their performances need to be further improved.In order to make the antennas have wideband,high gain and high efficiency performance and simple structure for processing,this paper studies and designs several terahertz circularly polarization antennas.The performance of the designed antennas is verified by simulation and measurement in this paper.The operating principle of each antenna is analyzed,and the calculation of circular polarized E-field is also proposed.This paper also designs and analyzes the application and performance of the design feed in terahertz system.The main research work of this paper is as follows:1.The operating mode of E-field in the elliptical waveguide is analyzed in the paper,firstly.A circular polarization feed based on the elliptical straight waveguide structure is designed.The circular polarization performance of elliptical structure is verified its ability in terahertz band by measurement.On this basis,a circularly polarized antenna with tapered elliptical waveguide is proposed.From 170 GHz to 260 GHz,the designed antenna achieves 41.84%of integrated impedance axial ratio bandwidth and 24.4-31.3 dBic of radiation gain.Furthermore,by optimizing the structure of tapered elliptical waveguide,an elliptical aperture pyramidal horn antenna is proposed.The operating principle of circular polarization is analyzed,and a calculation method of circular polarization radiation of elliptical aperture is proposed.2.Based on the circularly polarized antennas with elliptical structure,a horn antenna with rectangular aperture is proposed.In the paper,the operating principle of circularly polarize antenna with rectangular aperture is analyzed.And the calculation method of circular polarization radiation of rectangular aperture is given.In the range of 75 GHz to 110 GHz,the measured integrated impedance axial ratio bandwidth of designed antenna with rectangular aperture can reach 37.8%.A circularly polarized antenna with rectangular aperture of large aspect ratio is given.The integrated impedance axial ratio bandwidth of this antenna can reach 37%from 220 GHz to 320 GHz.A circular polarized antenna with two chokes is proposed,which can achieve the circular polarized flat-top radiation performance with amplitude fluctuation less than 1dB in the frequency range of 140 GHz to 150 GHz.3.For achieving the research objective of compact structure and easy machining,a fork shaped circularly polarized antenna is proposed.The measured antenna achieves 37.8%of the impedance axial ratio bandwidth in the range of 75 GHz to 110 GHz.A circularly polarized antenna with open slotted end structure is designed to achieve wideband circular polarization performance,and its structure is more compact.An embedded circularly polarized waveguide antenna based on quartz dielectric is simulated to verify the circularly polarized radiation performance in the frequency range of 90 GHz to 105 GHz.4.In the paper,the application and performance of the circularly polarized antenna in terahertz system are designed and analyzed.A dual circular polarization isolation system with ortho-mode transducer is designed.The elliptical aperture circularly polarized antenna and rectangular aperture circularly polarized antenna are used and analyzed in the system respectively.A Cassegrain antenna system with open slotted end circularly polarized antenna is designed,and the high gain circular polarization radiation performance is simulated.The influence of Cassegrain structure on the circular polarization performance is analyzed. |
PDF Full Text Request