Research On Dual-band Circularly Polarized Millimeter-wave Antenna

With the rapid development of the global Internet and mobile communication,the demand of mobile data services for network bandwidth is growing exponentially,so the 5th generation(5G)wireless communication technology emerges.5G system has the advantages of more than 10 Gbps transmission rate and less than 1ms transmission latency.The millimeter wave band in 5G system is divided into several unconnected bands.Due to the anti multipath effect of circularly polarized wave,the dual band circularly polarized millimeter wave antenna which is suitable for 5G system becomes the research hotspot.In this thesis,two types of millimeter wave dual band circularly polarized antennas with 5G operating bands are designed by studying the basic theory of electromagnetic radiation and reviewing the classical transmission line model and resonator model.1.A millimeter wave dual-band circularly polarized microstrip antenna based on Archimedes spiral radiation element is presented.By etching a ring gap on the bottom ground to tune the top radiation unit to generate upper band radiation,and connecting the inner circular patch and the outer edge of the ring gap with the embedded rectangular patch to match the impedance,the dual-band circularly polarized radiation in the millimeter wave band is finally realized.The simulation results show that the working bandwidths of the antenna are 1.05GHz(28.63-29.68GHz)and 2.35GHz(35.7-38.05GHz),respectively.The gains at 29 GHz and 38 GHz are 6.9d Bi and 6.6d Bi respectively,and the radiation efficiency is 90%.2.Due to the asymmetric structure of the front and back of the above antenna,the radiation pattern deviation angle is large,so a millimeter wave triple-band substrate integrated waveguide(SIW)antenna with dual-sense circular polarization is proposed.A circular slot is etched in the SIW resonator of TM210 mode to obtain an upper band radiator,and then a circular patch is introduced into the SIW circular slot to obtain a lower band radiator.A pair of notches are dug in the upper and lower band radiators to excite the orthogonal degenerate modes to realize circular polarization.Finally,the linear polarization radiation in the middle band is obtained by adjusting the coupling between SIW transmission line and circular patch.The proposed design first achieves circular polarizations at upper and lower band of 38 GHz and 28 GHz and linear polarization at middle band of 33 GHz.The measured results show that the gains of the antenna at three bands are 6.95 d Bi,7.90 d Bi and 8.91 d Bi respectively,and the efficiencies are higher than 91.8%.The proposed antenna has the characteristics of single feed,single-layer and low profile,which makes it a potential candidate antenna for 5G wireless communication system and network.