Research Of Circularly Polarized Antennas With Wide Beam And Oriented Beam

With the developments of satellite and mobile communication,circularly-polarized antennas are widely applied in many systems. Inglobal position system, antennas with wide beamwidth and high gain in thelow elevation are required to meet the requirement of SNR of the receiver.In base station system, the antenna array is usually selected to obtain theoriented beam, but its size is big to some special systems. Circularlypolarized oriented beam antenna with a tilted beam may be available to beused in engineering.The article begins with an overview of the background andsignificance of this study, sums up the current development of thecircularly-polarized wide beam and oriented beam antennas. Then thebasic theories of the circularized-polarized antennas are briefly described,containing the radiating principles of the circular polarization, the mainparameters of the circularly-polarized antennas and the main methods toobtain circular polarization.Circularly-polarized wide beam antennas have been designed based onthe existing technologies. Thereinto, circularly-polarized wide beammicrostrip antenna with air dielectric can obtain wide beam throughputting a strip line on the stacked shorted patch. The antenna achieves ahalf power beamwidth of120oin the frequency of3.75GHz-4.35GHz, a3dB AR (axial ratio) beamwidth of120o in the frequency of3.78GHz-4.22GHz. Circularly-polarized wide beam printed microstripantenna has broadened its3dB AR beam through a miniature feedingnetwork. Simulated and measured results show that the HPBW and the3dB AR beamwidth of the antenna are more than100oin the frequency of1.45GHz-1.58GHz. Finally, a circularly-polarized oriented beam antenna suitable for basestation system and a high gain circularly-polarized oriented beam antennasuitable for satellite communication are proposed. Circularly-polarizedoriented beam antenna adopts monofilar equiangular spiral and radiates atilted beam through altering the outermost circumference. The antennaachieve a frequency band range of24%for beam direction23°~25°. Thehigh gain circularly-polarized oriented antenna of satellite communicationexploits branch-line coupler to get CP radiation. The antenna has an ARbandwidth of10.3%and a gain of higher than8.1dBi.