The Realization Of The BroadBand Circularly Polarized Antenna Method Research

Circularly polarized(CP)antenna has many characteristics.Arbitrary line polarization waves can be received by it to avoid energy loss caused by polarization mismatch,and also to reduce multipath scattering,and will not be affected by Faraday rotation effect.Therefore,the antenna system of CP gets good reliability and stability,and it’s widely used in satellite communication,radio frequency identification,radar and other fields.In this paper,the realization method of the traditional CP antenna is reviewed,and three different ways are used to design the broadband CP antenna.The main contents are as follows:1.Circularly polarized crosseds-dipole antenna is designed based on single feed method.The main structure is composed of a pair of dipoles,90° phase delay ring,rectangular parasitic patchs,and a stepped cavity.The two dipoles are placed orthogonally on both sides of the dielectric plate,and the phase shift ring feeds the dipoles so that the dipole arms produce a phase shift of 90°.The coaxial inner and outer conductors feed the two sets of dipoles so that the four dipole arms achieve 0°,90°,180° and 270° phases in turn,thus realizing circular polarization.By adding rectangular patchs to the dipole arms expands,the bandwidth is expanded by introducing high frequency resonance points due to the self-resonance of the patch.The step cavity is designed to widen the low frequency bandwidth by extending the current path to produce low frequency resonance points,while gain’s stability is obtained.The final measured results show that the impedance bandwidth(IBW)and the axial ratio bandwidth(ARBW)of the antenna is 80.8%(2.03-4.78GHz)and 68.5%(2.35-4.8 GHz).In addition the good broadband CP performance is achieved,and the flat gain fluctuation is less than 1.5 d B2.L-shaped open slot circularly polarized antenna based on feed network.The antenna is consisted of the feed network and the slot antenna unit,which is fed from the center by coaxial.First,the L-shaped open gap antenna is designed with 5 GHz at the center frequency,and circular polarization was achieved by adjusting the microstrip feed position.The sequential rotating array antenna is composed because the sequential rotating arrangement can improve the CP performance.Next,a sequential rotating feed network with the same output power and 90° phase lag in sequence is designed.Finally,the array antenna and feed network are combined to realize the characteristics of broadband circular polarization.The final results show that the IBW and ARBW are 55.1%(3.43-6.04 GHz),33%(3.82-5.33 GHz),and the peak gain is 9 d Bic.3.Circularly polarized antenna based on polarization conversion metasurface(PCM).First,the principle of PCM of line to circular polarization is analyzed,and a double-loop slot type structure unit is designed.Then,the PCM array is loaded to the slot-antenna,which achieves a very low profile due to the common ground structure.The simulation results of IBW and ARBW is 24.3% and 20.3%,and the peak gain is 6 d Bic.To further broaden the bandwidth and also reduce the radar scattering cross section(RCS)by using the principle that the polarized super-surface of the mirror image structure can weaken the reflected waves,the front units are arranged in a rotating sequence and fed through the feed network.Finally,the simulation results of IBW,ARBW and the peak gain are 55.5%(3.31-5.85 GHz).30.7%(4.24-5.78 GHz),10.4 d Bic,and the antenna realizes RCS reduction.