Research On Optimization Of Subarray Partition For Phased Array Radar Antennas

Large phased antenna array are widely used in phased array radar systems. Considering the high cost and complexity of the system due to the numerous elements, it is necessary to use subarray partition techniques. The subarray configuration has a direct influence on the performance of array signal processing, however some simple subarray configurations are adopted in practice, which is lack of enough theoretical analysis and seriously restricts the overall performance of the radar system. Therefore, it is necessary to find the optimal subaray configuration for radar system design.A typical application of subarray partition is monopulse technique where the sum pattern is synthesized at the element level whereas the difference pattern is synthesized at the subarray level. The subarray technique can reduce the feed networks and hardware manufacturing cost. In order to synthesize both sum and difference patterns with low sidelobes, based on the excitation matching principle, the optimization model of subarray partition is established and aims at minimizing the matching error between the equivalent element weights and the reference low sidelobe element weights.Then, according to the optimal synthesis of sum and difference patterns for the linear array antenna, the subarray partition optimization is equivalent to a contiguous partition of ordered reference gain ratios. Therefore, a subarray partition method based on division position coding genetic algorithm is proposed in this paper. In this proposed method, the division position of ordered list is encoded as a chromosome gene, then the initial population is randomly generated by a series of non-repeated integers, and the fitness calculation and genetic operation are subtly designed to improve convergence and stability of the proposed method. According to the simulation results and analysis, it is shown that the proposed method can quickly converge to the optimal solution through global searching, and can obtain smaller excitation matching error and lower sidelobe level when compared to the uniform partition method.Meanwhile, according to the optimal synthesis of sum and difference patterns for the circular array antenna, the optimization of subarray partition can be reformulated into a clustering of the reference gain ratios, which can be solved by some traditional clustering algorithms such as K-means clustering. However, when the element weights are non-uniform for such specific intensions such as low sidelobes, the excitation matching error could not be minimized completely. Therefore to solve this problem, a subarray partition method based on modified K-means clustering algorithm is proposed in this paper, which can make full use of element weights and reduce the excitation matching error by modifying the cluster criterion and cluster center of the traditional K-means clustering algorithm. According to the simulation results and analysis, it is shown that the proposed method can obtain the minimum excitation matching error and the lowest sidelobe level when the elements are weighted non-uniformly.Finally, the whole paper is summarized and the further research of subarray partition techniques is provided in future works.