Design And Implementation Of Circularly Polarized Antenna Based On Eletromagnetic Dipole

As the signal receiving and transmitting part of the wireless communication system,the antenna is both the beginning of the system and the terminal of the system.The rapid development of communication technology also puts forward higher requirements on the performance of the antennas.In addition to achieving stable gain and pattern in the operating band,easy to process and low cost,but also requiring wider bandwidth and smaller size.Circularly polarized antennas have the advantage that traditional linearly polarized ant ennas are difficult to match because they can suppress multipath effects and reduce polarization mismatch.Today,they have been widely used in modern wireless communication systems such as satellite communications,global positioning,and radio frequency identification.This paper adopts the principle of complementary pattern of electric dipole and magnetic dipole to obtain an excellent antenna design,through studies on the realization of omnidirectional and directional circularly polarized antennas.The main research work completed is as follows:(1)A broadband left-hand circularly polarized omnidirectional antenna based on a current loop-electric dipole is designed.The impedance bandwidth and axial ratio bandwidth of the antenna have reached more than 20%.In the working frequency band,the left-hand polarization gain of the antenna is greater than 1d B,and the cross-polarization is greater than 15 d B.The omnidirectional radiation is realized in the horizontal plane,and the roundness is less than 1d B.(2)A left-hand circularly polarized antenna based on the current loop and magnetic current loop is designed.The height of the antenna is only 0.02max?.The impedance band is only 2%,but the antenna has excellent axial ratio characteristics,more than 10%.The left-hand polarization gain of the antenna in the working frequency band is greater than 1d B,and the cross-polarization is greater than 20 d B.The omnidirectional radiation is achieved in the horizontal plane,and the roundness is less than 1d B.(3)Next,a broadband low-profile left-hand circularly polarized directional antenna based on electromagnetic dipoles was designed.The impedance bandwidth of the antenna reached 33.7%,and the axial bandwidth was 22%.In the direction of maximum radiation,the gain in the antenna bandwidth is greater than 6.5d B and maximum gain is 7.8d B.The cross-polarization exceeds 20 d B.The directional patterns of the antenna and the E and H planes are symmetric and stable heart-shaped patterns.The beam width is greater than 600 and the front-to-back ratio is greater than 15 d B.(4)Two sets of electromagnetic dipoles are used to feed by two parts with a phase difference of 90 degrees.The impedance bandwidth of the antenna is 2.2%,and the axial bandwidth is 1.1%.The pattern of the E-plane and H-plane of the antenna are heart-shaped.In the maximum radiation direction,the gain in the antenna band is greater than 3d B and maximum gain is 4.6d B.The cross-polarization is greater than 15 d B.The bandwidth and gain are higher than the previous one which is the inevitable loss because miniaturization.The antenna has wide beam width that is greater than 1350.The front-to-back ratio is greater than 15 d B.The antennas are modeled,simulated and optimized by HFSS2019 electromagnetic simulation software.This paper makes a theoretical analysis of the designed antennas and describes the antenna design method and working principle.The antenna designed in this paper has the characteristics of broadband,low prof ile,miniaturization,high gain and stable radiation pattern.It can be widely used in mobile communication equipment.