Time Modulated Antenna Array Research And Applications

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 special filtering and improve the anti-interference ability of the phased array radar. 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. 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 main work of this thesis includes five parts as shown below:1. Based on the theory of time modulated antenna arrays, the thesis summarize three typical time schemes, including the Variable Aperture Sizes (VAS) scheme, the Unidirectional Phase Center Motion (UPCM) scheme and the Bidirectional Phase Center Motion (BPCM) scheme. Their advantages and disadvantages are also given.2. The genetic algorithm (GA) is employed to synthesize multiple patterns and suppress the sideband radiation in time modulated arrays.3. The time modulation approach is extended to planar antenna arrays with square lattices and circular boundaries to synthesize ultra-low sidelobe patterns. Comparing with those of the conventional arrays, the advantages are significant.4. A full-wave simulation approach in frequency domain of the time modulated arrays is presented, utilizing Ansoft Designer to obtain the patterns at central frequency and its near sidebands, analyzing the mutual coupling effect of the antenna elements in time modulated array.5. The harmonic components that generate in the time-modulated array are used to determine direction of arrival. If the array elements are switched by a waveform with variable markspace ratio, it is possible to electronically scan the angular location.