Study On Miniaturized Circularly Polarized Antenna With Broadband And Wid Beamwidth

Modern wireless communication environment is more and more complex.In order to have better communication quality,antennas need the performance of broadband,wide beamwidth and miniaturization.This thesis was research of circular polarized antennas for different application and requirement.Three kinds of antennas with different performances was proposed and the main work contents was summarized as follows:Firstly,a circularly polarized antenna with miniaturization and wide beamwidth was proposed.The antenna is divided into radiating element and feed elements.The radiating structure is a closed 3D spiral ring built on a PCB board which radiation performance is equivalent to a pair of orthogonally placed electronic and magnetic dipoles.Huygens source with wide beamwidth was obtained by the electric dipole and magnetic dipole has the directions radiation patterns in the E and H-planes.The radiation elements are fed by an open-ended and arc-shaped strip line to obtain equal magnitudes and successive 90° phase differences.The circularly polarized operating frequency of this antenna is 1.571-1.63 GHz.In addition,the corresponding gain,half power beamwidth,front-to-back ratio,and 3-d B AR beamwidth of the CPHSA are 2.85 d Bi,134°,36.5 d B,and 130°,respectively.The measured results for a prototype are in good agreement with the simulated results.Secondly,this thesis designs a broadband low-profile circular polarized antenna.The design of the antenna is based on a cross-dipole structure.Phases of the inner and outer cores of the coaxial cable are opposite to each other,and the microstrip line is used to perform phase shifting.Four trapezoidal patches are phase-shifted by 90° in phase and then fed in order.Circular polarization.An ordinary back-cavity structure floor is used,the antenna section is 32 mm,the circular polarization operating frequency is 2.12-3.55 GHz,and the relative bandwidth is 50.4%;then the square artificial magnetic conductor(AMC)structure is used as the floor,and after simulation optimization,the profile is reduced to 18 mm,and the miniaturization performance is obvious.This antenna has a circularly polarized operating frequency of 2.33-3.5 GHz,a relative bandwidth of 40.1%,a profile of only one eighth wavelength,and good broadband and miniaturization performance.Finally,starting from the broadband monopole antenna,this thesis proposes an asymmetrically fed broadband S-shaped circularly polarized antenna.The process is simple and using an FR4 dielectric board with a dielectric constant of 4.4 which fed by an asymmetric feed structure,where the microstrip feedline deviates a certain distance from the middle of the dielectric board.This structure causes the surface current of the floor to change and interact with the surface current on the monopole patch,which increases the bandwidth of the antenna and can appropriately reduce the structural complexity and size of the monopole patch.This antenna has a circular polarization operating frequency of 2-3.3 GHz,a relative bandwidth of 49.1%,an in-band half-power lobe width of about 100°,and a maximum gain of 2.05 d B.The antenna was processed and tested,and the results were in good agreement with the simulation results.The antennas designed in this thesis are all small-sized circular polarized antennas,which can obtain the performance of broadband or wide beamwidth with miniaturization.The principle of circular polarization generation and the test and simulation results are discussed in detail in the antenna design process.The reliability of the above three antennas was verified.