Investigation Of Millimeter-Wave Wideband And Multiband Reflectarray Antenna

The millimeter-wave wideband and multi-band reflectarray antenna has been widely required in the modern wireless communication system.The reflectarray antenna combines the high gain advantages of the array antenna and parabolic antenna.Meanwhile,there are some other merits such as light weight,small volume,low profile,low cost,etc.This dissertation mainly focuses on the difficulties encountered in wideband and multi-band reflectarray antenna design.To overcome the bandwidth problem of the reflectarray antenna,the phase response optimization method and multi-frequency phase compensation method are proposed.To overcome the multi-frequency design problem of the same-layer topology and dual-layer topology of the reflectarray antenna,the mutual coupling surpression method between the units and the blockage elimination method between the arrays are proposed.The main works are stated as follows:1.An approach of optimizing the element phase response is presented.Usually,the more resonant structures,the better broadband performance.However,the unit with complex structure are difficult to manufacture in the millimeter-wave frequency band.To address this problem,a millimeter-wave broadband high-efficiency single-layer reflectarray antenna with ability of phase-response restructuration is proposed.The three varied-size rings with fixed outer-loop are used to improve the simulation accuracy and suppress the coupling between the units.Partition optimization method is used to reconstruct the phase response of the cells.The restructured phase response curves have the better parallelism and linearity,which are useful to improve the working bandwidth and the aperture efficiency of the antenna.The experimental results show that the proposed design can effectively improve the broadband performance of the small-aperture reflectarray antenna.2.The multi-frequency phase compensation method based on partition optimization is prensented.With the reflectarray antenna aperture size increasing,the influence of spatial dispersion will not be ignored.It is difficult to effectively expand the antenna bandwidth by the traditional wideband design methods.To address this problem,this dissertation proposes a millimeter-wave large-aperture broadband reflectarray antenna with multi-frequency phase compensation capability.Different from the traditional broadband reflectarray antenna that only compensates the phase value at a single frequency,the elements in the aperture will compensate the required phase values in different frequencies,which is useful to suppress the spatial dispersion influence.Meanwhile,by optimizing the unit topology,it is useful to simple the unit design and to manufacture accurately in millimeter-wave band processing.The measured results show that the proposed method can effectively expand the working bandwidth of the large-aperture reflectarray antenna.3.An approach of designing dual-band reflectarray antenna with flexible frequency ratio in the same-layer is presented.To improve the aperture utilization of the traditional dual-band reflectarray antenna in the same-layer and suppress the mutual coupling between the units,this dissertation proposes a dual-band high-efficiency reflectarray antenna with a flexible frequency ratio in the same-layer based on structure-reuse technique.The reflectarray antenna consists of two sets of elements.One is the high-frequency cell with the square metallic waveguide structure,and the other is the low-frequency dipole cell excited by a substrate integrated waveguide(SIW).A pair of symmetry walls of the metallic waveguide in the x-polarization direction is replaced by the SIW-fed dipole cells,which is resultful to make full use of the radiating aperture.Both elements with large phase compensation ranges can suppress the mutual coupling effectively.The simulated and measured results of the proposed dual-band reflectarray antenna are in good agreement.The results successfully validate the effectiveness of the proposed method in the design of a millimeter-wave dual-band reflectarray antenna with the large frequency ratio.4.An approach of eliminating the blockage effect of the dual-layer dual-band reflectarray antenna is proposed.To address the mutual interference and the blockage of the traditional dual-layer dual-band reflectarray antenna,this dissertation proposes a dual-layer dual-band reflectarray antenna with coupling suppression ability based on structure-reuse technique.The reflectarray consists of two substrates and three metal layers.The top metallic layer is the Ka-band array composed of three-loop unit cells.The middle metallic layer is the Ku-band array consisted of cross-slot unit cells.The bottom metallic layer is the metal ground.Based on the structure-reuse technique,the reflected ground of the Ka-band element is replaced by the cross-slot structure.This method can reduce the mutual interference between different arrays and eliminate the blockage effect caused by the multi-layer structure.Meanwhile,the higher-band three-loop element is used as the parasitic structure for the lower-band unit,which is resultful to improve the phase compensation of the lower-band element.The experimental results show that the designed reflectarray antenna can work well in two bands.The method proposed in this dissertation is beneficial to improve the radiation performance of a dual-band reflectarray antenna with the large frequency ratio.