| The communication quality of systems is always determined by the performance of antennas,which are one of the most important RF devices at the end of wireless communication system.Due to the good rotational orthogonality,the antennas with circularly polarized characteristics can effectively eliminate the rotation effect of the ionosphere on the electromagnetic wave when receiving the circularly polarized waves with same rotated direction.Also,the interference of the rain fog and the multipath effect are attenuated.Especially in the satellite navigation communication system,in addition to the ability of receiving and transmitting signals with circular polarization,it is also expected for antennas to be insensitive to polarization position,realize wide beam coverage and obtain high gain at low elevation.Among the various technologies for achieving wide beamwidth performance of the circularly polarized antennas,since the effect of the method of loading a dielectric lens on the half-power beamwidth(HPBW)and axial-ratio beamwidth(ARBW)are always in conflict.Even if the directivity of the antenna becomes flat,its AR performance will be greatly affected,and the ARBW of the antenna will be reduced,thus it has been rarely used in recent years.Therefore,under the the support of the National Natural Science Foundation of China(Fund No.51809030),the application of lens-loaded technology in wide beam circularly polarized antenna is studied in detail in this paper,and the main achievements are as follows:(1)A novel dielectric lens-loaded circularly polarized antenna with wide 3 dB ARBW is proposed.In order to solve the issue of the narrow ARBW for traditional microstrip antenna with the infinite ground plane,the cylindrical dielectric lens with cone-shaped air cavity is designed to improve the AR performance and enhance the ARBW of the antennas.Firstly,by using the geometrical optical analysis method,the paper focuses on the changes of AR when the electromagnetic wave passing through different dielectrics and the specific expression of AR is given.Then,with the aid of HFSS simulator,the proposed antenna is modeled and the key parameters are discussed.Finally,in order to verify the effectiveness of this method,the antenna is fabricated and the various technical indicators are tested.It is depicted from the simulated and measured results that the 3 dB ARBW is widened from 82°(?=0°)/81°(?=45°)/80°(?=90°)to 160°(?=0°)/170°(?=45°)/164°(?=90°),nearly 80°increment of the 3 dB ARBW is obtained.This means the antenna obtains wide coverage of the upper half space and it can meet the basic requirements of the satellite navigation and positioning system.(2)A novel dielectric lens is proposed,which can improve the AR performance ulteriorly for the circularly polarized antennas with wide 3 dB ARBW.Similarly,the electromagnetic simulation software is used to discuss and analyze the related parameters,the feasibility of this design is verified by the fabrication and measurements.It is shown that by using the dielectric lens,the ARBW is enhanced from 206°?218°to 248°-252°.Also,the power radiation pattern of the antenna is invariable and the approximately spherical coverage of good AR performance for signals is realized in last.(3)A novel dielectric lens with a stacked cone-shaped cavity is proposed to broaden the HPBW and ARBW of conventional circularly polarized(CP)patch antenna with arbitrary dimensional ground plane.The effect on the phase delay of the electromagnetic waves in different directions is different under the utilization of the dielectric lens,then the radiation energy distribution in free space for antenna is changed.Hence,a uniform amplitude response is obtained and the HPBW is widened.The measurements show that by using the proposed lens,the HPBW of the CP patch antenna is extended effectively from 69°(?=0°)/69°(?=90°)to 170°(?=0°)/173°(?=90°)while maintaining a wide 3 dB ARBW of more than 200°,this means the antenna has excellent radiation performance of wide beamwidth. |
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