Array Antenna Synthesise Based On Active Element Pattern Method

The mutual coupling between array elements cannot be ignored when the array antenna radiation characteristic is analyzed. In recent years, the active element pattern method is widely used in the design of antenna array, which can effectively consider the mutual coupling effects on the array antenna radiation.Array antenna synthesis is an optimization problem with many variables and constraints. The parameters of this type of problem usually have the characteristics of non-differentiable even discontinuities and the optimization of pattern parameters is a non-linear problem. Traditional optimization methods search for the best solutions using gradients or random searching. Gradient methods are efficient, but have disadvantages of working only on continuous and differentiable parameters and involving a fewer objective variables. Random search doesn’t require gradient calculations, but tends to be slow and susceptible to getting stuck in local optima. Intelligent optimization algorithms developed in recent years only require that the objective functions can be calculated rather than requiring the parameters with differentiable or continuous characteristics. The optimizing process of the algorithm is in line with certain directivity to search the global optima and the optimizing ability is favourable.This thesis mainly studies on the applications of the active element pattern method and intelligent optimization algorithms in the array antenna designs. The work is shown in the third, fourth, and fifth chapters.In the third chapter, the effectiveness of active element pattern method used in analyzing the regular antenna array’s radiation characters is firstly verified. Then the method is used to analyze the radiation characteristics of a middle-sized linear antenna array, and the genetic algorithm is applied to optimize the array elements’ excitation current amplitudes and phases. Several practical array patterns are obtained.In the fourth chapter, a new method is proposed for applying the active element pattern method to analyze the radiation characteristics of thinned linear antenna arrays. Simulation results confirm the effectiveness of the proposed method. A modified immune algorithm is completed in order to improve the synthesis effectiveness of thinned linear antenna array, and is combined with the proposed active element pattern method to design thinned linear antenna arrays. Finally, simulation and numerical results are given to verify the effectiveness and superiority of the design method.In the fifth chapter, a new method for synthesizing large antenna arrays is proposed. This method effectively applies intelligent optimization algorithms to synthesize large antenna arrays with arbitrary aperture shapes and element grids. Thus the disadvantage of premature convergence is eliminated when using intelligent optimization algorithms to directly synthesize large antenna arrays. Simulation results are given to verify the effectiveness of the proposed method.