Research And Design Of A Circular Polarized Helical Dipole Antenna With High Gain And Wide Bandwidth

Axial mode helical antenna is a kind of circular polarized(CP)antenna with excellent performance,which is widely used in satellite communication,global position system(GPS)and radio frequency identification(RFID).However,there are more number of turns and higher profile in the traditional axial mode helical antenna,which makes it difficult to meet the needs of the miniaturization of terminal communication device.The aim of this paper is to realize the low profile,wide bandwidth and high gain of the helical antenna.And the specific research content and achievements are as follows:1?Firstly,a radiating element with a symmetrical bimetallic helical strips is studied,and a strip-helical dipole antenna operating in the UHF band is designed.By means of a Wilkinson power divider and a 180° phase shift network,two symmetrical distributed metallic helical strips are subjected to equal amplitude inverse excitation,so that the whole helical antenna works in the dipole mode.Compared with the single-armed helical antenna,the working mode of the helical dipole can significantly increase the antenna gain and reduce the cross polarization.In addition,due to the symmetry and complementarity of the radiator,the symmetrical characteristic of radiation pattern is greatly improved.And the measured results show that the antenna's circular polarization axis ratio bandwidth(AR<3dB)is 65%(0.53-1.04GHz),and the maximum gain is 11.2dBi and stable.The size of the antenna is 0.56?0×0.56?0×0.56?0,and the profile height is greatly reduced compared to the conventional axial-mode helical antenna.2.Based on this helical dipole antenna model,a helical dipole antenna operating in 5G millimeter wave band is designed.The wide-band impedance bandwidth(73%,21-45GHz)and the circular polarization bandwidth(70%,21.4-44.5GHz)in millimeter wave band are achieved,which can effectively cover the operating frequency band of 5G millimeter wave band.And the electromagnetic simulation results show that the average gain of the antenna in the operating frequency band is stable at 10 dBi or more,the front-to-back ratio is greater than 15 dB,and the overall size is about 0.47?0×0.47?0×0.66?0.3.Based on the above 5G millimeter wave helical antenna element,a 2×2 planar phased antenna array is designed.Through the sequential rotation method of array elements,the mutual coupling effect between the array elements is greatly reduced,thereby obtaining an ultra-wide circular polarization bandwidth(74%,23-50 GHz).At the same time,the beam scanning characteristics of the antenna array are analyzed.By controlling the phase of the excitation element,the conical area scanning function of the main beam in the range of-14° to+14° is realized.