| With the rapid development of the electronic countermeasures and the requirement of detecting and tracking space targets, phased arrays are widely applied in modern radar technologies. In order to improve the anti-interference ability of the phased array radar, one of the most important requirements is the low/ultra-low sidelobes of the phased arrays. Pattern synthesis of conventional antenna arrays for low/ultra-low sidelobes usually generate very high excitation dynamic-range ratios, which result in difficulty in practical engineering implementation. On the other hand, the time modulated antenna arrays introduce a fourth dimension– time– into the design, which consists of simple"on-off"switching of antenna elements in a predetermined sequence. Thus, they can be used to control the aperture excitations more freely and more easily to realize low/ultra-low sidelobes. Associated with relevant research projects, this thesis is just to focus on some aspects of the hardware implementation of the time modulated antenna arrays, including the following three parts:Firstly, based on the requirements of designing a broadband and low sidelobe array element, a novel double-layered printed dipole with integrated balun is presented. The novel dipole antenna was designed using the commercial software HFSS, fabricated and measured. Reasonably good agreements between the simulation and measurement results are obtained. Measurement results indicate that the bandwidth of the antenna is up to 62%, while the cross-polarization level is less than -37dB.Secondly, an S-band 16-element linear array of the double-layered printed dipole antenna is designed. Measurement results verified the broadband and low cross-polarization properties of the array.Finally, the low sidelobe array pattern synthesis was studied. Some theoretical and experimental studies on low sidelobe phased array beam steering and the low sidelobe patterns from uniform amplitude time modulated linear arrays are also carried. |
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