| As the rapidly development and widely application of modern wireless communication technologies,higher requirements for miniaturization,high speed,integration and multi-function have been put forward.Reconfigurable antenna can change the frequency,polarization,and pattern by means of electronics,machinery,materials,etc.,which can greatly improve the overall performance and is beneficial to the miniaturization and intelligence of the system.Therefore,the research on reconfigurable antenna has important theoretical and practical significance.This dissertation focuses on the topic of "Key Technologies of Reconfigurable Antennas and Arrays for Wireless Communication Systems" and the main research works are as follows:1)A design method for wideband pattern reconfigurable antenna is proposed,and two types of antenna array are implemented.Firstly,an antenna element with a relatively bandwidth of 13.6% is proposed by adopting a substrate integrated cavity and a parasitic patch layer.Two feed ports are introduced and a 180° phase difference can be achieved by individually excitation with the two ports.A 2?2 antenna array is designed based on the antenna element.The pattern of the antenna array can be switched by controlling these feed ports.Secondly,in order to get a wider bandwidth and more beam states,the antenna element is modifed and the antenna array is expanded to 4?4.The modifed antenna element consists of a parasitic patch layer,a drive patch layer,and a feed network layer,and the two switchable feeding probes.The 4?4 antenna array is capable of switching between different beams with a stable radiation property and a relative bandwidth of 21.4%.Relevant works have been published in IEEE Access and international conference of IEEE IMS 2017,and a patent has been applied.2)Four design methods for polarization reconfigurable antennas are proposed,and the corresponding antennas are implemented.Firstly,a cavity-backed slot antenna with two switchable shorting pins is proposed.When the perturbation is appropriate,circular polarization(CP)will be achieved by two orthogonal modes with equal amplitude and 90°phase difference.When both the two shorting pins are OFF,the antenna will operates in linear polarization(LP)state.A 2?2 antenna array is designed based on the antenna element.By controlling the state of each antenna element,the polarization of the antenna array can be switched among LP,left-hand CP(LHCP)and right-hand CP(RHCP)state.Secondly,a 2?2 antenna array consisting of four LP antenna elements rotated 90° in turn is developed for more polarization states.By controlling the states of each antenna element,the polarization of the antenna array can be switched between two LP,LHCP,and RHCP states.Thirdly,in order to reduce the cross polarization level on the chamfer plane,a metasurface antenna,which mainly comprises a patch layer,a feeding network layer,a metasurface layer and four feed ports,is proposed.By controlling the four feed ports,two LP,LHCP,and RHCP states are realized.The antenna has a wide bandwidth and good polarization purity.Morevoer,the cross polarization level on the chamfer plane is effectively suppressed.Finally,two pairs of switchable electric dipoles are introduced on basis of end-fire CP antenna.By controlling the state of the two pairs of electric dipoles,the polarization of the antenna can be switched between LHCP and RHCP.Based on the proposed antenna element,a 1?2 antenna array is developed using two antenna elements placed back-to-back.By controlling the state of each antenna element,the polarization of the antenna array can be switched between LHCP and RHCP,and the polarization characteristics of the bidirectional radiation are the same.Relevant works have been published in IEEE Trans.on Antennas Propag.,IEEE Access,IEEE Antennas Wireless Propag.Lett.,international conference of IEEE ICUWB 2016 and IEEE IWAT 2017,and two patents have also been applied.3)A design method of frequency polarization reconfigurable patch antenna is proposed,and the corresponding antenna is implemented.Firstly,by introducing controllable shorting pins in the square patch,the resonant frequency can be changed due to the inductance effect of the shorting pins.Secondly,two pairs of controllable perturbation patches are introduced in the four corners of the square patch.By controlling the states of the two pairs of perturbation patches,the polarization of the antenna can be switched between LP,LHCP and RHCP states.Hence,according to the different control states,the operating frequency and polarization state of the antenna can be reconfigured independently.The proposed antenna has good polarization purity and a stable peak gain with a fluctuation value of 1.8 dB for all operating states.Relevant works have been published in IEEE Access,and a patent has been applied.4)A design method of polarization pattern reconfigurable antenna is proposed,and the corresponding antenna array is implemented.Firstly,the spatial rotation phase shifting technique is proposed,which can be used to realize CP beam switchable antenna with an expanded axial ratio(AR)bandwidth.Secondly,a three-port CP reconfigurable antenna element is designed,which mainly includes parasitic patch layer,driving patch layer and feed network layer.A 90° or 180° phase shift can be realized by selecting different feed ports.Two pairs of controllable chamfers are introduced into the drive patch and the polarization can be switched by controlling its state.Finally,based on the antenna element,a 2?2 antenna array is realized.By controlling the feed port and polarization of each antenna element,the radiation beam and polarization of the antenna array can be dynamically reconfigured among nine beams and dual CPs.Moreover,when the main beam is switched from normal to other directions,the AR bandwidth is significantly improved.Relevant works have been published in IEEE Trans.on Antennas Propag.and the international conference of IEEE IWS 2018,and a patent has been applied. |
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