Design And Study Of Miniaturized And Circularly-polarized Ultra-wideband Antennas

With the rapid development of ultra-wideband(UWB)wireless communication technology,antennas are required to have characteristics such as broadband,miniaturization,and circular polarization.The broadband antennas can meet the high transmission rate requirements of UWB communication systems.The miniaturized antennas are for ease of the internal integration of communication systems.The circularly polarized antennas have the advantages of anti-electromagnetic,such as electromagnetic interference,cloud and rain weather and multi-path effect interference,which can satisfy the stability requirements of the communication system.In this dissertation,therefore,the researches on the frequency extension,miniaturization and circular polarization of antenna technology have been carried out.The contents of the work are as follows:(1)In view of the communication system's requirements for antenna miniaturization and UWB characteristics,a miniaturized UWB microstrip antenna for 5G communication and WLAN is presented.To achieve the characteristics of broadband and miniaturization,the cross-shaped slots and circular defects ground structure are respectively embedded in the radiating patch and ground plane.Moreover,the implication of the parasitic patch realizes the impedance match.The results show that the proposed microstrip antenna has the characteristics of broadband and miniaturization.More precisely,the proposed antenna can operate in the frequency range of 3.28-6.38 GHz,e.g.the relative bandwidth is 64.2%.The radiation direction of the antenna is stable in the same band.Besides,the antenna was tested,and the measurement and simulation results are in good agreement.(2)To meet the demands of the communication system for antenna circular polarization and UWB characteristics,a circularly polarized UWB antenna for S-band is designed.To realize the miniaturization of antenna,the circular slot is embedded in the radiating patch.Then,we design a pair of perturbation branches at the diagonal corners of the patch to excite the orthogonal working mode,so that the antenna radiates circularly polarized waves.Based on the antenna,branch loading is carried out at the feed structure to improve the impedance matching.Besides,we test the properties of the antenna.The results show that the relative bandwidth of the antenna is 52.8%(2.42-4.12 GHz),the 3 dB axial ratio bandwidth is 25.9%(2.88-3.74 GHz),and the radiation direction of the antenna is stable.