Research On Dense Multi-port Antennas And Arrays For Time-reversal Electromagnetic Systems

Time-reversal(TR)electromagnetic systems have wide application prospects in high-capacity communication systems,super-resolution imaging systems,microwave power combination systems,and other systems,because the time-reversed electromagnetic wave has the property of synchronous space-time focusing.In this dissertation,antennas and arrays,as the necessary devices in TR systems,are researched.According to the positions of the antennas and arrays in TR systems,this dissertation has three sub-directions,which are the wide-angle scanning array at the position of transmitters,the dense multi-port antenna at the position of receivers,and the electromagnetic regulating array in propagating environments.The main contents in this dissertation are introduced in the following.In the first part,the dense multi-port terminal antennas used in TR systems are in-depth investigated and a series of new principles and novel methods are proposed,such as the TR-based radiator-sharing approach,the dispersion division multiple access technique for TR systems,and the dielectric transformation principle for the design of TR dense multi-port antennas.Firstly,the radiator-sharing approach is presented to design the dense multi-port antenna,which can make full use of the design space and support several ports with different functions.Afterwards,two kinds of multi-path single-radiator antennas,i.e.,radiator-overlapped multi-path antennas,are proposed based on a dispersion division multiple access technique and the volume of the antenna used in TR systems is further reduced.Finally,a novel TR super-resolution focusing method based on the dielectric transformation is proposed and a double-port dielectric antenna is designed based on this method.Each port of the dielectric antenna has a good independent focusing property in TR electromagnetic systems.In the second part,the wide-angle scanning arrays in TR electromagnetic systems are systematically studied,a series of academic problems,such as the one-dimensional wide-angle scanning,the two-dimensional wide-angle scanning,and the bidirectional wide-angle scanning,are solved,and the effectiveness of the theoretical analysises and the practicability of the proposed methods are verified with design examples.Firstly,for the one-dimensional wide-angle scanning application,eight basic antenna types which can be used in wide-angle scanning arrays are analysed based on the mirror theory.Then,a wide-beam antenna and a one-dimensional wide-angle scanning array are designed based on the “electric current parallel to magnetic wall” model.Afterwards,a three-magnetic-current model is presented to generate the hemispherical pattern and a two-dimensional wide-angle scanning array is designed based on the three-magnetic-current model.Finally,a two-magnetic-current antenna with a bidirectional radiation pattern and a sparse array are presented.The sparse array can adaptively generate a single beam and multiply beams in TR electromagnetic systems and has a wide-angle scanning property in two end-fire areas.In the third part,the electromagnetic regulating arrays used in TR systems are in-depth researched and a series of novel techniques are proposed,such as the localized-mode metasurface-based TR focusing noise deduction technique and the Huygens metasurface-based TR transmission enhancement technique.Firstly,a scanning metasurface array is proposed based on the localized mode of defective photonic crystals.The scanning metasurface array can be used to enhance the TR subwavelength focusing and decrease the electromagnetic noise in focusing areas.Afterwards,a reflected metasurface array is presented to regulate the scattering environment based on the Huygens principle.The Huygens metasurface array can dramatically increase the transmission efficiency in TR electromagnetic systems by using the feedback regulation mechanism.The research in the dissertation indicates that the dense multi-port antennas used in TR systems can be realized by designing the scattering structure and dispersion structure;the wide-angle scanning arrays used in TR systems can be realized by designing wide-beam elements;the electromagnetic environment regulation can be enhanced and the TR electromagnetic system can have a better performance by combining the TR-based time-domain electromagnetic regulation technique and the array-based space-domain electromagnetic regulation technique.