Research And Design Of Circularly Polarized Microstrip Antenna With Wide Beam

With the rapid development of satellite communications and mobile communications,the antenna as an important part of the communication system,its performance determines directly the quality of the entire system,so higher requirements are put forward for the radiation characteristics of the antenna.Because the circularly-polarized antenna is isolated from each other on the left and right circularly-polarized waves,and when the circularly-polarized wave is incident on a symmetrical target,the rotation will be reversed,so it has a weaker multipath effect and strong suppression of rain and fog interference and other characteristics,that is why the satellite navigation and positioning system generally use circular polarization wave as a satellite navigation signal.In order to receive more satellite signals,the satellite navigation and positioning systems require that the antenna not only has wide angle range with low axial ratio,but also has a larger space range and a higher low elevation gain.The dissertation mainly focuses on the research of wide beam circularly polarized microstrip antenna.It begins with an overview of the background and significance of this study and the current development of the circularly-polarized wide beam antennas,and sums up some methods of broadening the beam width of the antenna.The generation conditions of circularly polarized wave are analyzed emphatically.Based on the principle of single-feed method and high frequency structure simulator(HFSS),a microstrip antenna with simple structure and good circular polarization performance was designed and manufactured.Simulated and measured results show that the axial ratio is less than 2dB in the GPS operating frequency band,and the low axial ratio beam almost covers half the space in the main planes,and the half power beam width is 98°,those results satisfy the design requirement.The influence factors of the beam width are analyzed,and the methods of widening the beam width are studied.After the principle analysis and software simulation,two antennas with wide beam width are designed,and the double-layer antenna with metal ring extends the 3dB beam width effectively by combining the main radiation unit with the strongest vertical radiation and the parasitic ring with strong horizontal radiation.The optimal design shows that the antenna has a 3dB beam range of more than 140° in the vertical main planes and AR is less than 3dB in the beam covering space,and the maximum gain is-0.9dB.The antenna loaded metal cylinders can effectively widen the beam width of the antenna to 140° by the electromagnetic coupling betweenthe radiation patch and the parasitic monopole and AR is less than 2dB in the beam covering space.The antenna profile can be effectively reduced by loading the metal disk at the top of the metal cylinders,and the maximum gain is 3.2dB and the average gain at 10° elevation is greater than-0.5 dB.