Investigation On Pattern Reconfigurable Antennas And Their Arrays

With the development of information technology and intelligent technology,both wireless communication and military electronics are accelerating their evolution towards intelligence.Therefore,the new generation of wireless systems has raised higher demands and expectations for antennas.Pattern reconfigurable antennas have multiple controllable radiation states,they can not only adaptively switch beams according to the scenarios and users but also intelligently manipulate the radiation characteristics.Thus,it is a hot topic at present.However,traditional reconfigurable antennas/arrays have certain shortcomings and challenges in terms of sizes,cost,and radiation control capabilities.Therefore,they are not suitable for intelligent wireless communication applications,such as 5G/6G,intelligent Internet of Things（Io Ts）,and satellite Internet systems.According to these mentioned challenges and issues,this work focuses on novel reconfigurable antennas/arrays.And,this dissertation proposes new high-performance radiators,develops new reconfigurable methods,and expands the scope of digitally-modulated antennas.These works will help to enhance the experience of intelligent wireless technology from both theoretical and technical perspectives.The main research contents of this dissertation are summarized as follows:1.For short-distance scenarios（microcell and indoor environments）,miniaturized aperture-shared pattern reconfigurable antennas are proposed.First of all,by integrating a zeroth-order resonance（ZOR）metasurface and multiple mushroom-type reflectors,a novel compact reconfigurable radiator is designed.Here,the radiation source and reflectors are utilized equivalently,which leads to an ultimate low to a quite lower profile（0.05λ₀）and achieves vertically polarized（VP）multi-beam switchable radiation.Subsequently,this aperture-shared reconfiguration method is transferred to a horizontally polarized（HP）antenna.Based on the split-ring resonator（SRR）,this HP reconfigurable antenna not only has an extremely compact aperture（0.31λ₀×0.31λ₀）but also achieves three-beam scanning in the horizontal plane.Compared to traditional Yagi-Uda designs,the proposed aperture-shared reconfiguration method effectively solves long-term problems,such as large sizes,dispersed structures,and complex control networks.2.To address the shortcomings of traditional designs such as limited beam states,inevitable radiation blind areas,and poor beam-scanning capacities,a novel multi-mode phase control method is proposed.Firstly,a dual-mode multi-beam antenna is proposed.By combining a pair of odd and even modes,this dual-mode antenna can achieve four different beams（such as complementary and tilted beams）,which can effectively eliminate radiation-blind areas.Then,in order to further explore the potential of mode control,a tri-mode 360°continuous beam-scanning method is creatively proposed.By controlling the excitation phases of three orthogonal modes of the radiator（VP,right-handed circular polarization,RHCP,and left-handed circular polarization,LHCP）,the360°continuous beam-scanning is well realized in the horizontal plane.Based on this smart design,the problems of limited beam states and poor beam-scanning capacities can be effectively solved.Moreover,the overall antenna is extremely simple without any parasitic structures.This novel multi-mode phase control method opens a new approach to designing high-performance reconfigurable antennas.3.For long-distance communication and detection scenarios（macro stations,satellite communications,and radars）,novel Huygens-based reconfigurable antennas and wide-angle beam-scanning arrays are proposed.Firstly,a miniaturized Huygens source radiation mechanism and its reconfigurable methods are presented.By introducing the mirror source idea,the size of the Huygens source is directly reduced by half.Then,this work develops an electric-dipole（E-dipole）reconfigurable Huygens source and a wide-angle beam-scanning reconfigurable linear array,respectively.By only using five reconfigurable array elements,the 3 d B beam-scanning range is enhanced from[-35°,+35°]to[-70°,+70°],which partially solves the inherent problems of large sizes and high cost in traditional designs.Subsequently,due to the symmetry,a magnetic-dipole（M-dipole）reconfigurable Huygens source and a wide-angle beam-scanning planar array are designed,respectively.Owing to the multi-beam reconfigurable array element,this 4×4array can achieve a wide-angle beam-scanning capacity of±60°on the two-dimensional plane.And,this design provides a new method for wide-angle beam-scanning planar arrays.In addition,a novel hybrid metamaterial structure is realized by mixing the metamaterials and dielectric resonators,which not only reduces the whole profile but also improves the radiation performance.Generally speaking,this section develops many new innovative designs on reconfigurable Huygens antennas/arrays,including but not limited to broadband hybrid metamaterial,miniaturized Huygens source,multi-functional E-dipole/M-dipole reconfigurable elements,low-cost wide-angle beam-scanning linear array（1-D array）,and compact reconfigurable planar array（2-D array）.4.To meet the demands of intelligent wireless communications and solve the limitations of traditional digitally-modulated arrays,novel intelligent reconfigurable arrays are proposed based on the above-mentioned innovative works.Firstly,a multiple-component digital modulation array mechanism is proposed,which discretizes electromagnetic components such as phase,polarization,and amplitude.As a result,the radiation characteristics of the electromagnetic wave are digitally manipulated.Then,a phase and polarization digitally-modulated array is designed,which achieves spatial diversity and polarization diversity by selecting different digital coding sequences.And,this design can significantly improve radiation modulation capabilities and enhance channel capacity.Then,in order to further expand the beam-controlling capability,a new higher-bit digital beam-controlling method is presented.And,this design can achieve rich radiation control functions such as±50°single-beam continuous scanning,multi-beam switching,and beamforming.Owing to the polarization reversal principle of the TE₁₀mode and the phase shifting characteristics of the metasurface,a 2-bit phase&1-bit amplitude digital radiator is realized by using only 3 switch elements（minimum）.By combining higher-bit digital elements and higher-order mode structures,this intelligent reconfigurable array not only achieves flexible beam-controlling capabilities but also provides a new solution for low-loss large-scale arrays.In this section,the scopes of digital modulation have been well expanded,and these innovative digital modulation designs can serve as an important supplement to digital metasurfaces（Reconfigurable intelligent surface,RIS）.Therefore,these works can become good candidates for the new generation of intelligent wireless communication.