A reconfigurable antenna array design whose array elements can move along a semicircular path to synthesis radiation patterns is proposed. This movement is simply carried out by stepper motors without using any other actuators. The array factor of the new design is derived in order to construct the objective function and solve the optimization problem of required pattern synthesis. To validate the design, array patterns with single, symmetric double, multiple, and wide nulls are computed by only controlling element rotation angles with a quantized differential evolution algorithm. The results show that the obtained patterns fit in the restriction masks successfully. The method presented in this letter can also provide both symmetric and asymmetric patterns since the array elements have a freedom of movement in two dimensions.

A backtracking search optimization algorithm (BSA) is proposed for the synthesis of concentric circular antenna arrays (CCAAs) with the low sidelobe levels at a fixed beamwidth. Several numerical examples of CCAA patterns with the single, multiple, and broad nulls imposed at the directions of interference are also given to illustrate the performance and flexibility of the proposed algorithm. BSA is a relatively new population based evolutionary optimization algorithm. The numerical results show that the design of CCAA using BSA provides good sidelobe levels with a fixed beamwidth. The nulling patterns obtained by BSA are also very good. The quality of results obtained by the BSA is checked by comparing with that of several metaheuristic algorithms in the literature. BSA is also compared with differential search (DS) and bacterial foraging algorithms (BFA) in terms of iterative performances.

Differential search (DS) optimization algorithm is proposed for the synthesis of three different types of linear antenna array design examples. The first group of examples is that DS algorithm is used to locate wide nulls on the linear antenna array patterns by controlling amplitude-only. In these examples, sidelobe levels disposed to rise are also suppressed by using DS algorithm in the same optimization process. In the second group of examples, individual nulls are placed with the help of DS algorithm by controlling the amplitude-only, phase-only, and position-only. The last example is a linear antenna array failure correction example. In order to tolerate the element failures, DS is employed to recalculate the amplitude values of the remaining intact elements of the antenna array. The results show that DS is very capable to solve the linear antenna array optimization problems which have different characteristics.

In this article, a quantized water cycle algorithm (QWCA) is used for the antenna array pattern synthesis with low side-lobe levels (SLLs) and nulls at desired directions by using four-bit digital phase shifters. In addition to the standard features as a metaheuristic algorithm, QWCA has an internal quantization mechanism and a precalculated array factor method. The latter provides an accelerated procedure to QWCA under favour of the digitized values that can be stored in a three-dimensional array. This acceleration is based on the reality that the accessing data in the memory need less time than the usage of the mathematical functions throughout the optimization process. The internal quantization mechanism of QWCA is utilized to achieve digital values matching to the discrete values of the phase shifter instead of the simple rounding up/down routines after optimization. The numerical results showed that QWCA can obtain very good SLLs and null depth levels (NDLs) on the synthesized pattern. Moreover, the results are achieved in remarkably short optimization times. SLL and NDL values obtained by QWCA are also compared with the available literature values. The comparisons reveal that QWCA is able to produce better results than the other compared alternatives. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:21–29, 2015.

An efficient variant of differential evolution (DE) algorithm, namely subpopulated differential evolution (subDE), is proposed for solving null synthesis problems of time-modulated circular antenna arrays by controlling time intervals and phases. The capabilities of subDE algorithm are examined by comparing its convergence curves and number of successful optimizations to those of the classical DE. Wilcoxon rank-sum test is also applied to ensure that the results are significant in terms of statistics. Furthermore, the antenna array parameters achieved by using subDE are compared to those of the classical DE in the literature. The results show that subDE can exhibit better performance than the classical DE for our antenna array synthesis examples. Additionally, the simulations are executed on an embedded microprocessor to investigate if subDE can also run on such a limited environment. The results demonstrate that the contemporary embedded systems hold promise for evolutionary algorithms.