Abstract
Smart antennas are capable of improving signal transmission or reception by adapting the desired radiation pattern in response to environmental or operational changes. The adaptive nature can be achieved with an array of radiating elements controlled by smart signal processing algorithms. An adaptive array improves the radiation pattern by adjusting the weights of array elements to get the desired signal and attenuate the undesired signals. Conventional antenna arrays can generate desired radiation patterns with the optimization of three main parameters such as amplitude, phase, and position of the array elements. The traditional arrays have a high dynamic range ratio (DRR), and it also increases the complexity of the array feeding network. Phase shifters are used in conventional arrays to steer the main beam in desired direction which implies higher insertion loss and quantization errors. To overcome these issues, the complexity of the conventional array synthesis methods is greatly reduced with a new dimension—“Time,” as an additional control parameter of antenna radiation characteristics. This chapter deals with the applicability of “Time-domain” array synthesis method towards a smart way of designing antenna arrays implemented by RF switches. The simple ON-OFF switching mechanism of timed arrays can be controlled with high-speed RF switches to enhance the adaptability and reconfigurability of the array. In this chapter, different applications of timed arrays are explored. Pattern synthesis for interference rejection, beamforming, and beam steering are analyzed with optimal switching sequences. Other parameters such as excitation amplitude and spacing between the radiating elements are also optimized for some applications. Towards this purpose, a wavelet mutation-based differential evolution algorithm (DEWM) is used. Other familiar meta-heuristics algorithms like particle swarm optimization (PSO) and real-coded genetic algorithm (RGA) based results are presented for comparison.
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