| Array antenna can easily realize high gain,beam scanning and beamforming,which has become the main means of transmitting and receiving signals in modern wireless communication,navigation,radar and other information systems.In order to meet the demands of high data rate,wide coverage and multi-function for modern wireless information system,array antenna is required to have wide working bandwidth and wide-angle beam scanning capability,and also take into account the characteristics of planar structure,low-profile and multi-polarized radiation.To deal with these requirements and challenges,this dissertation takes expanding the working bandwidth and beam scanning range of array antenna as the research topic.From the perspective of the mutual coupling control between array elements,researches on the weakly coupled resonant array antenna and the tightly coupled quasi traveling wave array antenna are carried out.Through a series of explorations from theoretical modeling,implementation methods to experimental verification,important research progress has been made.The main research works of this dissertation are summarized as follows:1.The influence of the mutual coupling between wide-angle impedance matching(WAIM)layer unit cell on its performance is explored.Simulation analysis shows that the wide-angle impedance matching characteristics can be realized in a wider working bandwidth by utilizing the mutual coupling.Then,the WAIM layer is loaded on the top of the tightly coupled array antenna to achieve good wideband wide-angle scanning ability of the array antenna,which showing its great research prospects in the wideband wide-angle scanning phased array antenna.2.The wideband working mechanism of metamaterial-based antenna is deeply analyzed and a variety of novel miniaturized wideband metamaterial-based antenna elements are proposed,and an effective method to expand the working bandwidth of wide-angle scanning phased array antenna based on resonant element is developed.Based on the metamaterial unit cell dispersion characteristics,H-plane,E-plane and two-dimensional miniaturized wideband metamaterial-based antenna elements are proposed and applied in grating-lobe free wide-angle scanning phased array.By elaborately designing the feeding structure,good impedance matching is achieved for the miniaturized element.In addition,the scanning blindness caused by surface wave coupling in E-plane linear array antenna is eliminated by DGS structure.Besides,the feeding structure is further modified to eliminate the backward radiation in two-dimensional scanning.Finally,over 20%bandwidth and±60°scanning range with low gain fluctuation are realized in linear array antenna and two-dimensional planar array antenna.These proposed metamaterial-based array antennas significantly improve the working bandwidth of the traditional wide-angle scanning phased array antenna which based on the resonant principle.3.A low input impedance wideband connected parallel slot array antenna based on the tightly coupled quasi travelling wave concept is proposed,and the idea that directly integrating the WAIM layer into the array antenna aperture is also proposed.In this way,a wideband wide-angle scanning phased array antenna with ultra-low profile is realized,which effectively overcomes the problem of using complex wideband balun and high-profile WAIM layer in the traditional tightly coupled array design.By adding a parasitic slot to the traditional connected slot array,its input impedance is reduced,and combining with the metasurface that directly loaded on the array aperture,connected parallel slot phased array antenna of 2:1 bandwidth and±60°conical scanning range is achieved.Meanwhile,the array antenna profile is only approximately 0.088?_L,where the?_L relates to the free space wavelength corresponding to the lowest working frequency.In order to further understand and demonstrate the working mechanism of the parasitic slot and the metasurface WAIM,the equivalent surface impedance of the connecting slot array unit cell and the WAIM unit cell are respectively extracted.Unit cell transmission line equivalent circuit models of the radiation slot,the parasitic slot,the metal reflector and the ultra-thin WAIM are established and verified by the full wave simulation results,which provides a concise and high-precision analysis method for this kind of array antenna.4.The infinite magnetic current sheet concept is applied to wideband circularly polarized array antenna,and combining with the image theory,an ultra-wideband low-profile unidirectional circularly polarized connected parallel slot array antenna is proposed.By adopting connected parallel slot structure,two orthogonally arranged equivalent magnetic currents are built.Three-fourths ring phase shifter is adopted to introduce appropriate phase difference between these two orthogonal equivalent magnetic currents.As a result,circularly polarized array antenna with AR bandwidth of2.4:1 is achieved.For the sake of suppressing the back radiation,a metal reflector is added and boresight gain of array antenna is improved to approximate the ideal aperture directivity.5.Based on the fully polarized dipole concept,a polarization insensitive antenna element and its wide-angle scanning array antenna are proposed to improve the communication link stability between transceiver antennas under random orientations.The quasi full space full polarization coverage is realized by constructing three pairs of approximately equal amplitude orthogonal current distribution by bending dipole antenna,and it is experimental verified in human wireless endoscope system application.Then,with the aid of time reversal adaptive beamforming technology,the polarization insensitive wide-angle scanning performance of the random array composed of 25elements with random orientation and random position is studied.Finally,the polarization insensitive beam scanning characteristics of±85°and±60°are respectively achieved by the random array in free space and over an infinite ground plane. |
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