Researches On Wide-Angle Scanning And High-Gain Planar Arrays

Compared with the individual antenna,there is more freedom for the array antenna to realize beam scanning,beam forming,multiple beams,high-gain radiation,and so on.While the planar phased array antenna scans its main beam,the scanning angle is limited and the gain fluctuation is large due to the structural constraint and some other reasons,such as the coupling's influence,which are urgent academic problems to be solved.With the development of the fifth generation mobile communication technology,the millimeter-wave communication becomes one research hotspot currently.The data rate can be highly improved by the millimeter-wave communication,but the millimeter wave suffers from the high propagation loss in the space and the limited propagation distance.How to improve the gain and efficiency of the millimeter-wave antenna thus to enlarge the efficient distance of the millimeter-wave communication is another urgent academic problem.In this dissertation,the research object is the planar array antenna.The research mainly focuses on the challenges of the wide-angle scanning,low peak-gain fluctuation while scanning,and high-gain high-efficiency radiation of the millimeter wave.Some feasible solutions are come up with.The dissertation is arranged as follows:Chapter 1 firstly reviews the history of array antennas.Then,summarize current challenges for array antennas.Summarize the academic research backgrounds and the research significance.Also,introduce primary methods to design wide-angle scanning phased arrays and typical examples of planar millimeter-wave high-gain arrays.Finally,show the innovation points and major contributions of this dissertation.Chapter 2 introduces how to use parasitic structures in the planar wide-angle scanning microstrip phased array antenna and phased array feeding network.Firstly,design a microstrip dipole 1×6 linear array with uniform element's spacing and increase its scanning range by parasitic strips.On the condition that the array layout and element size don't change,parasitic strips are introduced among elements.The size and position of the parasitic strips have significant effects on the element's mutual coupling,then the fed element's active element pattern is influenced.So,the array's scanning angle in the elevation plane is greatly increased.Secondly,based on the parasitic structure,a phase shifter is designed to modify the output signal's phase,which is achieved by simple mechanical movement.For the phase shift structure,the basic idea is to overlay the microstrip line with a high-permittivity and low-loss dielectric slab,so the efficient permittivity and propagation constant of the microstrip line are varied.Dielectric slabs with different sizes on different microstrip lines can achieve output signals of progressive phase shift when these microstrip lines are parallel fed by the same input signals.By two-stage phase shift structures,the value of the progressive phase shift can be widely changed and,in the meantime,the change step can keep small.The designed feeding network can achieve twenty-five phase-shift states and good phase shift performances.In chapter 3,the differential feeding scheme is applied to the phased array antennas,which can improve the wide-angle scanning performance of planar phased array antennas.Firstly,the planar wide-angle scanning phased array is based on the pattern reconfigurable patch antenna as the element.As for the element design,slots are constructed on the ground of the patch antenna.PIN diodes are introduced to control the states of the slots and change the main beam's direction of the antenna's radiation pattern,so the efficient coverage of the radiation pattern in the E-plane is enlarged.Because of the differential feeding scheme,the radiation pattern of the antenna maintains symmetric and low cross-polarization at the same time.The array can achieve wide-angle scanning of the main beam with low peak-gain fluctuation and low cross-polarization.Secondly,a dual-band and planar wide-angle scanning phased array is designed based on the cavity slot antenna.The antenna is with dual-layer substrates and a metalized cavity formed by the metalized vias.The slot's radiation and the differential feeding scheme ensure that the antenna can be low profile.The antenna can resonant at two frequencies and the antenna's radiation pattern in the E-plane can achieve wide-beam coverage,be symmetric and be low cross-polarization.For the antenna in the array,the active element pattern can achieve wide half power beam width(HPBW)in the E-plane.At both resonant frequencies,the phased array can realize wide-angle scanning about the elevation angle in the E-plane.In chapter 4,by incorperating the aperture antenna,the array theory,and the array's feeding method,a high-performance 60 GHz array antenna is designed.Firstly extend the physical aperture of the original aperture antenna.The original radiation aperture is used as the element and arrayed on the extended aperture.The series feeding scheme is applied to the apertures by the transmission line and the radiation of the reverse electromagnetic field is avoided,so the gain of the aperture antenna is improved.The electromagnetic field's distribution on the aperture becomes more compact,so the aperture efficiency is improved.Also,optimizing the position and size of the radiation aperture and the size of the transmission line is needed for the antenna,which is fed by the differential feeding scheme.The millimeter-wave antenna can achieve high gain,high aperture efficiency,wide band,stable radiation pattern and low cross-polarization.In chapter 5,the summary of the main content in the dissertation is shown.The future research contents and applications about the planar wide-angle scanning array and planar high-gain array are presented.