We have proposed a new architecture for an array in which the elements are placed on a spiral curve in order to obtain an ultra wideband (UWB) radiation pattern. In addition, array factor and bandwidth of the proposed spiral array are calculated. Simulated results obtained by SuperNEC and CST software have shown good agreement with the analytic calculations. Although the proposed antenna array is wideband in nature, it lacks desirable efficiency, due to poor front to back ratio (FBR) and sidelobe level (SLL). In this paper, we have chosen three different approaches in order to improve the e±ciency of proposed array. First, the effect of length and thickness tapering of elements has been studied. Second, we have used Genetic Algorithm (GA) to optimized pattern shape. Finally, the influence of metamaterial cover on array performance has been investigated. Although the first and second methods improve the radiation pattern, the array bandwidth is reduced. It is shown that the third method improves array directivity and FBR by 5-7 dB and 15-17 dB respectively within the frequency band of operation.
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