Study On Wideband/Wide Beamwidth Circularly Polarized Antennas

After nearly one hundred years of development,wireless communication technology has been widely used in various fields,which made the antenna technology develop rapidly during this period.Compared with linearly polarized antennas,circularly polarized antennas can not only receive circularly polarized waves with the same direction of rotation,but also receive linearly polarized waves with arbitrary polarization,which have the advantage of eliminating polarization mismatch.In addition,circularly polarized antennas cannot receive the circularly polarized waves in the opposite direction of rotation.This polarization isolation property makes them have the advantage of suppressing multipath effects.Satellite communication and radio frequency identification and other fields need to overcome the problems of polarization mismatch and multipath effects,which makes circularly polarized antennas very popular in these fields.Due to the requirement of practical engineering applications,widening the bandwidth and beamwidth of circularly polarized antennas has become two very important directions in the research of circularly polarized antennas.After studying and drawing on the previous research results,this paper proposes a broadband circular polarization antenna and a wide beamwidth circular polarization antenna.1.This paper proposes a broadband circularly polarized crossed-dipole antenna with a hook-shaped radiator.The antenna adopts vacant-quarter ring feed structure.The hookshaped radiator is obtained by subtracting two ellipses of different sizes,the lengths of its inner and outer curves are approximately equal to 3 times and 2.5 times the dielectric wavelength at the center frequency of 6.5GHz,which provides a sufficiently long flow path for the surface current of the radiator,thereby exciting the traveling wave current and broadening the circular polarization bandwidth.The antenna uses a cylindrical metal back cavity to replace the traditional flat ground,and it also has the effect of widening the bandwidth while achieving unidirectional radiation of the antenna.Simulation results show that the antenna achieves 94%(3.51-9.69GHz)impedance bandwidth and 85%(3.80-9.42GHz)3d B axial ratio bandwidth.2.This paper proposes a wide beamwidth circularly polarized crossed-dipole antenna with a metasurface.By covering the basic circularly polarized crossed-dipole antenna with a layer of crossed shape metasurface to achieve the purpose of broadening 3d B axis ratio beamwidth.The metasurface unit is composed of a dielectric substrate,an upper metal patch and a lower metal square ring.When the electromagnetic wave passes through the metasurface,it is equal to the current flowing through the parallel circuit of a capacitor and an inductor.When the antenna works at the resonance frequency of the metasurface,the insertion loss of the metasurface is almost 0d B,so the metasurface almost does not affect the performance of the impedance bandwidth and axial bandwidth of the antenna below.However,the metasurface can change the distribution of the electric field amplitude in the far-field region,so that the field patterns of the two crossed dipoles in the same vertical plane are more similar to achieve the purpose of broadening the 3d B axis beamwidth.The test results of the wide beamwidth circularly polarized crossed-dipole antenna with metasurface are basically consistent with the simulation results.The antenna achieves a 3d B axial ratio beamwidth of 142° at a center frequency of 1.575 GHz,which can be applied to global satellite navigation systems.