Research On Novel Wide Beamwidth And Reconfigurable Circularly Polarized Antennas

With the rapid development and popularization of mobile satellite communications,global satellite navigation system(GNSS),wireless communication consumer electronics,and the intelligent communication network to be built,the broadband and wide beamwidth circularly polarized(CP)antennas have become the preferred front-end devices for this kind of multi-network interconnection terminal system,because of their wide signal bands,wide angular beam coverages and good circularly polarized radiation performance.In this dissertation,following practical application requirements,a series of researches on widebeamwidth circularly polarized antennas are carried out,and some novel miniaturized,wideband,dual-polarization,and reconfigurable circularly polarized antennas have been proposed.Main contributions of this dissertation can be summarized as follows.1.The wide-beamwidth CP microstrip antenna is studied.First,two methods for miniaturizing the microstrip patch are proposed.One is to reduce sizes of the radiation patch by loading capacitive substrate integrated impedance surface(CSIIS)inside the dielectric substrate,the other is to extend the current paths and reduce sizes of the patchs by etching radial gaps on surfaces of the radiation patches.These two methods are used to reduce the radiation aperture and broaden the axial ratio beamwidths of the antennas.Then,a novel wide beam CP microstrip antenna(MPA)is designed by combining these two methods.The experimental results show that the 3-d B axial ratio(AR)beamwidths of the designed antenna shows good circular polarization performance in almost whole upper half space.2.The dual CP antenna based on the SIW back cavity square slot is studied.First,a method for miniaturizing SIW cavity structure is proposed.A compact slow-wave structure with SIW back cavity is design by loading the CSIIS into the SIW cavity,which reduces volume of SIW cavity by 30.1% compared with the traditional structure,and miniaturizes of SIW cavity structure.Then,a novel dual CP antenna based on the SIW back cavity square slot is designed by etching square slot on the cavity surface and introducing feed probe into the cavity.This antenna achieves high front-to-back ratios in both polarization states.3.The wide beamwidth CP antenna based on SIW-back cavity slot is studied.First,a two-port sequential rotating(SQR)feeding network with high isolations is designed by the cascade connection of two Wilkinson power dividers and two ring couplers.Then,a pair of orthogonal slots is etched on the back cavity surface of SIW,and the wide beam characteristics of the orthogonal slots are analyzed.The designed feeding network is also cascaded with SIW-back cavity orthogonal slot,and a new wide ARBW dual-circularly polarized antenna based on the SIW back cavity slot is designed.Measured results indicate the beamwidths of the antenna in two polarization states are wider,and the isolations between two ports are higher.4.The wide-band and wide-beam CP multi-dipole antenna is studied.First,the influence of structural evolution of four multi-dipole antennas on their axial ratio beamwidths is analyzed and discussed,and a new three-dimensional topological structure with cross orthogonal arrangement is proposed.Then,according to this topology,multiple dipole patches are conformal with the dielectric carrier,and metal rings are loaded on the antenna,and an umbrella-shaped broadband wide-beamwidth CP antenna is designed.In the design of this antenna,the patch dipole is used to replace the traditional dipole,and the antenna impedance bandwidth(IBW)is widened by increasing the dipole arm diameter.Through further analysis and research of this topology,a CP antenna with wide bandwidth and axial ratio beamwith based on hemispherical structure is designed.Finally,the two designed antennas are fabricated and tested to verify effectiveness of the proposed method.5.The polarization reconfigurable planar magneto-electric(ME)dipole antenna is studied.First,the characteristics of complementary planar ME dipole element are analyzed.Then,the adjustable PIN diode is embedded between the electric dipole arm and the feeding phase shift line,and different radiation current paths of the electric dipole are selected to adjust the diode on-off states,thus realizing of the circular polarization reconfiguration.At the same time,based on this reconfigurable unit cell,three reconfigurable CP antennas are designed,which are the planar end-fired bidirectional CP reconfigurable antenna,the omnidirectional radiation CP reconfigurable antenna,and the hybrid pattern and polarization reconfigurable antenna.The reconfigurable design ideas of these three antennas are consistent.The measured results show that these three antennas have good reconfigurable CP characteristics.