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This paper presents a gradient-based optimization method for interference suppression of linear arrays by controlling the electrical parameters of each array element, including the amplitude-only and phase-only. Gradient-based optimization algorithm (GOA), as an efficient optimization algorithm, is applied to the optimization problem of the anti-interference arrays that is generally solved by the evolutionary algorithms. The goal of this method is to maximize the main beam gain while minimizing the peak sidelobe level (PSLL) together with the null constraint. To control the nulls precisely and synthesize the radiation pattern accurately, the full-wave method of moments is used to consider the mutual coupling among the array elements rigorously. The searching efficiency is improved greatly because the gradient (sensitivity) information is used in the algorithm for solving the optimization problem. The sensitivities of the design objective and the constraint function with respect to the design variables are analytically derived and the optimization problems are solved by using GOA. The results of the GOA can produce the desired null at the specific positions, minimize the PSLL, and greatly shorten the computation time compared with the often-used non-gradient method such as genetic algorithm and cuckoo search algorithm.

In this paper, a design optimization method for left-handed materials with specific frequency bands is proposed. A microstructure of the left-handed material is constructed based on the transmission line theory, and the properties of this material are simulated numerically with the S-parameter retrieval method and analyzed with equivalent transmission line model. The effects of the size parameters of the microstructure on the left-handed characters are analyzed. The analysis results verify that this structure does exhibit left-handed characteristics with appropriately sized microstructure. Then the mathematical model of the microstructure with maximized frequency band-width and lower loss at given frequencies is proposed, and examples are given. The design result confirms that the optimized model is applicable and accurate.

In this paper, based on the equivalent transmission line model a method of designing left-handed metamaterials micro-structures is proposed, verified and analyzed. Firstly, according to the basic transmission line model with left and right-handed characteristics, we build a new left-handed model by analogy. Then according to the qualitative analysis of the corresponding relationship of each component in the transmission line network to the shape and size of continuous medium micro-structure configuration, the specific size of model is inferred, and thus a reasonable left-handed metamaterials micro-structure configuration and the corresponding transmission line model are established. We have conducted a series of tests including numerical simulation, which verifies that there does exist the left-handed characteristic in a certain frequency band. Finally based on the numerical simulation and experiment the effects each micro-structural parameter on left-handed frequency position and bandwidth are analyzed, and the size parameter that affects the left hand characteristic most seriously is determined.