Design Of Circularly Polarized Antenna Array And Research On Its Performance Improvement Technology

With the rapid progress of technology,the application of wireless communication has also achieved unprecedented development,and antennas play a crucial role as an important component in wireless communication.Compared to linearly polarized antennas,circularly polarized antennas have the advantage of strong anti-interference ability.In recent years,in order to achieve better communication quality,the circular polarization and array of antennas have received increasing attention.At the same time,circularly polarized antenna arrays with low profile,high gain,wide axial ratio bandwidth,wide axial ratio beamwidth and other excellent characteristics have also become the current research focus.Based on the traditional circular-polarized antenna array,this thesis studies the gain,axial ratio bandwidth and axial ratio beamwidth improvement of antenna by gap decoupling technology,Spoof surface plasmon polariton(Spoof SPP),Spoof localized surface plasmon(Spoof LSP)and chiral metastructure respectively.The main contents of this thesis are as follows:1.A 2×2 circularly polarized antenna array based on L-shaped gap decoupling is designed.Firstly,a sequential-phase feed network based on Wilkinson power divider and phase shifter is proposed,and the radiation patches are excited by the feed network to form a two-layer 2×2 circular polarized antenna array.On this basis,L-shaped gap is introduced in the radiation patches to improve the axial ratio deteriorated by the coupling between the upper radiation patches and the lower feed network.The impedance bandwidth of the antenna is 1.68 GHz to 3.31 GHz,and the relative bandwidth is 65.2%.The axial specific bandwidth is 1.86 GHz to 3.39 GHz,and the relative bandwidth is 61.6%.Peak gain reaches 7.13 d Bic at 2.7 GHz.2.Two circular polarized antenna arrays based on Spoof SPP and Spoof LSP are designed.Antenna Ⅰ is a double-layer structure,the lower layer is a phase-shift feed network and the upper layer is radiation patches,and the two layers are connected by four metal probes.In order to further improve antenna gain and broaden axial-ratio beamwidth,Spoof SPP and Spoof LSP are introduced on the basis of the antenna array,and their local ability to electromagnetic wave is used to enhance radiation so as to improve antenna gain and axial-ratio beamwidth.Based on antenna Ⅰ,antenna Ⅱ adjusts the distance between the upper and lower dielectric substrates,and introduces Spoof LSP to improve the axial ratio deteriorated by the small spacing between the two layers.The measurement results show that antenna Ⅰ can reach 72%(3.15～6.75 GHz)measurement impedance bandwidth and 55%(3.97～6.72 GHz)measurement axial ratio bandwidth,and the peak gain is 11.11 d Bic.Antenna Ⅱ achieves 71.8%(3.14～6.73 GHz)measurement impedance bandwidth and 53.2%(4.10～6.76 GHz)measurement axial ratio bandwidth,with a peak gain of 12.05 d Bic.These two antennas have the advantages of small size and high gain.3.A circular polarized antenna array based on chiral metastructure is designed.The antenna is divided into two parts,and the inside is a double-layer circular polarized antenna array.The feed network adopts three dimensional(3D)form,that is,part of the feed network is placed vertically to the lower dielectric substrate to reduce the coupling between the feed network and the radiation patches.The outer frame is a periodic arrangement of chiral metastructure units,which have good circular dichroism in the 4.9～5.2 GHz frequency band.Therefore,the differential absorption of LHCP and RHCP by chiral metastructure is used to improve the axial-ratio beamwidth of antenna.In addition,the metal on the back of the frame also enhances the reflection,which effectively increases the gain.The measured impedance bandwidth of the antenna is 80%(2.81～6.81 GHz),the axial ratio bandwidth is 70.8%(3.68～7.22 GHz),and the peak gain is 15.28 d Bic.The results show that the gain and axial-ratio beamwidth of the target antenna can be improved by introducing the chiral metastructure into the designed circularly polarized antenna.