| As the available spectrum resources in the microwave low frequency band become less and less,the millimeter wave frequency band has been widely studied due to its advantages of abundant spectrum resources,less interference and wider bandwidth.Antennas are necessary components for transmitting and receiving signals in communication systems.The line-of-sight transmission characteristics of millimeter waves have new requirements for antennas in terms of gain,sidelobes,and beam steering capabilities.The antenna feeding part of the traditional phased array technology is huge and complex,resulting in low degree of freedom and high cost of the antenna system.Beam switching technology can realize the beam steering function of traditional phased array antennas,enabling the design of low-cost antennas with beam steering capabilities.In this thesis,the beam-switchable conformal array antenna is applied in the 5G millimeter-wave frequency band,and the beam switching control is realized by loading the routing network,which can realize the omnidirectional radiation of the H-plane of the array antenna.It has far-reaching significance to realize wireless coverage in complex network environment.The specific work content of this thesis is as follows:1.Design of millimeter-wave cross-feed linear array antenna.The cross-feed structure is designed by using the patch inversion method,and the linear array antenna is designed by combining with the Taylor synthesis method.The antenna sidelobe is-24.21 d B and the gain is16.59 d Bi.The performance of linear array antennas with three different feeding methods is compared.The Taylor linear array with cross-feeding method has the largest bandwidth and the lowest sidelobe level at the same time.In addition,the bandwidth of the millimeter-wave crossfed linear array antenna is widened by the loading of the perturbation structure,and the bandwidth of 400 MHz is widened to 1 GHz on the basis of maintaining the characteristics of low sidelobe level.2.Design and Analysis of Millimeter-Wave Cross-Feed Array Antenna Beam Switching.According to the principle of beam switching,a design scheme of beam switching based on the surface of the cylindrical carrier is proposed,which combines RF semiconductor switches to achieve beam control.The antenna layout is determined by the normalized performance index of omnidirectional coverage of the antenna,and a 5*8 miniaturized array antenna with H-plane omnidirectional coverage is designed by studying the conformal performance of the cross-feed linear array on a small radius cylinder.Five groups of linear array antennas are arranged at equal intervals along a 20 mm radius cylinder,and the array direction is parallel to the cylindrical busbar.Only one group of antennas is excited individually each time.The isolation of each port of the beam switching antenna is less than-40 d B,the E-plane exhibits high-precision radiation characteristics,the half-power beamwidth(HPBW)is less than 13.11°,the H-plane HPBW is greater than 73.8°,and the antenna gain is as high as 16.23 d Bi.3.Construction of switching control circuit for millimeter wave cross-feed beam switching antenna.The beam switching circuit is built based on the radio frequency semiconductor switch(RFSS)chips ADRF5027 and ADRF5045.The antenna array is controlled by the routing switch of the RFSS,and the equiangular omnidirectional beam switching of the antenna is realized.The integrated PCB of the RF switching circuit and the antenna is used to reduce the size of the antenna switching system.Finally,the correctness of the wide beam switching design of the cylindrical conformal array antenna is verified by the space radiation characteristic test in the microwave anechoic chamber.The establishment of the beam switching technology of the cylindrical conformal array can effectively broaden the switching range of the beam switching antenna,and also provides a wide range of application prospects for the conformal antenna. |
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