Time Modulated Antenna Array Theory And Applied Research

With the rapid development of modern radar technology, the requirements of the radar systems on their respective antennas becoming more and more stringent. Phased arrays are often adopted in many phased array radar systems, and one of the most important requirements is the low/ultra-low sidelobes so as to achieve good spacial filtering and improve the signal-noise ratio. However, conventional arrays for low/ultra-low sidelobes usually have very high excitation dynamic-range ratios, which result in stringent error tolerance requirements in practice. If an additional degree of design freedom - time– is introduced into conventional arrays, which forms the time modulated antenna arrays, the low/ultra-low sidelobes can be achieved with a lower excitation amplitude ratios. This is of more importance in practical engineering. The time modulated antenna arrays consist of simple on-off switching of antenna elements, which make the aperture average excitations vary within the modulated period and thus have great flexibility in the control of the aperture excitations. Consequently, it is relatively easier to use them to realize low/ultra-low sidelobes.Focused on the time modulated antenna array, the main work of this thesis includes four parts as shown below:Firstly, the related research background is reviewed, including the pattern synthesis of conventional antenna array, the fundamental theory of the time modulated antenna arrays, low/ultra-low sidelobe pattern synthesis from time modulated antenna arrays, and sideband patterns, etc.Secondly, the differential evolution (DE) algorithm is employed to synthesize multiple patterns and suppress the sideband radiation in time modulated arrays.Thirdly, a full-wave simulation approach in frequency domain of the time modulated arrays is presented, utilizing HFSS to obtain the patterns at central frequency and its near sidebands. Simulation results are compared with published measurement results.Finally, the time modulated arrays are full-wave simulated in time domain, using the Finite Difference Time Domain (FDTD) method. The far-field signal and patterns at central frequency and each sidebands are then obtained through transformation.