In this paper, Side Lobe Level Reduction (SLL) and control of beam broadening in beam steered linear array of isotropic radiators with uniform inter-element spacing was investigated. As a solution to the problem of beam broadening with reduced SLL, a novel method was proposed modifying primarily the search space definition in Classical Particle Swarm Optimization (CPSO). In the proposed method, search space for CPSO was defined using different amplitude distributions, namely, Chebyshev distribution, Taylor one parameter distribution and Taylor Chebyshev error distribution. CPSO, with the information of where to search, finds the optimum excitation amplitude within defined search space for achieving both reduced SLL and narrow beam width. As an example, a 16-element linear array was considered to obtain both reduced SLL and beam width narrowing within the beam steering range. The results showed the effectiveness of the proposed method.

Synthesis of linear antenna array pattern has been the subject of many investigations and studies (Schelkunoff, 1943; Dolph, 1946; Taylor, 1953; Kennedy and Eberhart, 1995; Ratnaweera et al., 2004; Balanis, 2005; Mailloux, 2005; Zhang et al., 2008; Abusitta et al., 2009; Sayidmarie and Plumb, 2010; Chatterjee et al., 2013a; 2013b; and 2013c). One of the primary synthesis problems is to achieve Side Lobe Level (SLL) reduction, where Dolph (1946) introduced a novel technique using Chebyshev polynomial to obtain equal SLL pattern. The resulting array pattern is named Dolph Chebyshev linear array or simply Chebysev linear array. Consequently, Taylor (1953) gave a monotonically decreasing array pattern. Both methods resulted in linear array with unequal excitation amplitude and main beam at broadside position.

In phased array, one of the major requirements is to have an antenna array system with beam steering capabilities or to have null placement capability in a particular direction along with beam steering. There are two generic approaches to beam steering: dynamic phased array beam steering and adaptive beam steering. In dynamic phased array beam steering, the main beam is placed towards desired direction (Balanis, 2005; and Mailloux, 2005). In dynamic array, feed to each element is varied in such a way that the received or transmitted signals from all the elements are in phase in a given direction (Balanis, 2005; and Mailloux, 2005). The value of phase in that case depends upon the main beam position.

Telecommunications Journal, Side Lobe Level Reduction (SLL), Classical Particle Swarm Optimization (CPSO), Beam steered linear array, Side Lobe Level (SLL) reduction, First null beamwidth, Particle Swarm Optimization (PSO).