Research And Design Of Wideband Circularly Polarized Patch Antenna

As a kind of converter to transmit and receive electromagnetic wave,antenna is a very important part of radio communication system.Circularly polarized antennas stand out due to their remarkable anti-rain and fog interference and anti-multipath effects,as well as the advantages of orthogonality of rotation,strong ionospheric penetration,and little influence by the Faraday effect of the earth's two-pole magnetic field.Because of its low profile,small size and easy to realize multi polarization,microstrip antenna has become the main choice to design circularly polarized antenna,but the general circularly polarized micro strip antenna has a narrow bandwidth.Meanwhile,the emergence of broadband antennas meets the requirements of radio communication for system capacity and information transmission rate.In order to have the advantages of broadband,circular polarization,and microstrip,this master's dissertation designs three types of broadband circular polarization microstrip antennas,which are summarized as follows:1.A wideband circularly polarized patch antenna is proposed in this master's dissertation.The semicircular radiating patch of the antenna rotates 135 degree along the+x axis and is connected to the 50? microstrip feed line via an impedance converter.The tilt of the radiating patch and the coupling between the radiating patch and the ground plate produce circularly polarized waves.The working bandwidth of the antenna is expanded by slotting on the ground plate.Taking the antenna as a unit,a pair of 2×2 antenna array is formed through continuous rotation and translation.The simulation results show that the VSWR?2 impedance bandwidth of the unit and its array has reached 74.3%and 93.6%,respectively,while the 3dB axial ratio bandwidth is 65.5%and 100%.2.A wideband circularly polarized microstrip antenna based on cross dipole structure is designed in this master's dissertation.Two of the four cross dipoles are connected by quarter wavelength phase-shifting lines,and are placed on both sides of the dielectric substrate.The circular polarization performance of the antenna is improved by loading parasitic patches and improving the linear dipole.Then use the designed antenna as a unit to obtain a 4×4 square array of broadband circularly polarized antennas.Finally,the VSWR?2 impedance and 3dB axial ratio bandwidth of the antenna unit are 62.1%and 46.5%respectively,and the ActiveVSWR?3 impedance bandwidth of the antenna array is 75.5%.3.A circularly polarized antenna that works in the UHF frequency band is proposed in this master's dissertation.And based on the UHF frequency band antenna,a common-aperture antenna that works in the S and UHF frequency bands is designed.The main material of the designed UHF band circular polarization antenna is all metal,and the antenna adopts a four-port feed point excitation method to achieve circular polarization.The final antenna ActiveVSWR?3 impedance relative bandwidth is 38.5%,and the 3dB axial ratio bandwidth reaches 50%.Using the previously proposed antenna array that works in the S band,a common aperture antenna is designed by placing UHF band antenna and S band antenna array in different layers.When the antenna works in the UHF frequency band,the ActiveVSWR?3 impedance relative bandwidth of the antenna is 21.6%,and the 3dB axial ratio bandwidth is 22.2%.When the antenna works in the S band,the ActiveVSWR?3 relative bandwidth of the antenna impedance reaches 68.6%.