A Study Of Pattern Synthesis For Large Planar Arrays

As the information transfer mode of satellite communication, terrestrial microwave relay and various military and civilian radars, wireless transmission plays an increasing important role since the rapid development of science and technology. Known as an equipment of radiating and receiving radio waves, antenna plays a pivotal role in wireless system and directly affects the performance characteristics of the system, so it is critical to design an antenna fully meets the demands.Due to the rapid development and the wide application of wireless communication technology, it needs antenna own a higher performance. High-performance antenna can not only relax the requirements of the system, but also improve the overall performance of the system. It needs antenna with a high gain, wideband omnidirectional, flat-topped and shaped beam pattern. Moreover, it requires antenna with a small electrical size, light weight, low cost and simple structure. Since a single antenna cannot fully meet the increasing requirements, antennas are often distributed as arrays. Therefore, seeking for an efficient, simple and stable pattern synthesis algorithm has been the focus of the antenna field. Thanks for the wide azimuth and elevation scanning capability, high gain and easy realization of three dimensional beamforming, large planar arrays obtain a wide range of application.The thesis is carried out by combining with relevant research projects on the synthesis of large planar arrays, and it can be roughly divided into three parts:Firstly, the fast pattern synthesis method for large periodic planar arrays is studied. After establishing the Fourier relationship between the element excitations and the array factor, the alternating projection method based on the fast Fourier transformations can quickly synthesize the array pattern to the required. Since the low convergence of the conventional alternating projection method, two improved projection operators are proposed to synthesize the periodic rectangular grid array and the periodic arbitrary triangular array respectively. Detailed examples verify the fast convergence and short computational time of the modified operators.Secondly, the pattern synthesis approach for large unequally spaced planar arrays is researched. Thanks for the nonuniform Fourier relationship between the element excitations and the array factor, a fast pattern synthesis approach for the nonuniform array is presented. The main idea is that the nonuniform array is interpolated into virtual uniform array, and then the alternating projection method based on the fast Fourier transformation can be used to synthesize the pattern of the uniform array to the required. The remain is to calculate the element excitations of the nonuniform array by the transformation matrix established between the uniform array and the nonuniform one. Specific example proves the feasibility and the correctness of the interpolation.Finally, theoretical research of the time-modulated arrays and the application on the synthesis of the arrays are considered. By introducing the additional time dimension into the design of the array, it reduces the dynamic range of the amplitude of the element excitations leading to a simple complexity of the feeding network.