LLMS Adaptive Array Beamforming Algorithm for Concentric Circular Arrays

An improvement of Signal-to-Interference Ratio (SIR) at the base station of a wireless communication system can be obtained using a suitable choice of an array antenna. In this paper we consider Concentric Circular Antenna Array (CCAA) which can be used for adaptive antenna systems. A new adaptive algorithm, called least mean square-least mean Square (LLMS) algorithm, has been proposed for different applications of array beamforming. Unlike earlier LMS algorithm based techniques, the proposed algorithm derives its overall error signal by feeding back the error signal from the second LMS algorithm stage (LMS2) to combine with that of the first LMS algorithm section (LMS1). In this paper, we employ the LLMS beamforming algorithm for a CCAA system. The mathematical model of CCAA is analyzed. Computer simulation results show that employing LLMS algorithm is superior in convergence; and beam pattern performances over earlier LMS based algorithms. Furthermore, CCAA LLMS beamforming is more robust compared with other algorithms when operating in the presence of Rayleigh fading. Fidelity of the recovery signal of all algorithms under test is demonstrated by means of the resultant values of Error Vector Magnitude (EVM) and scatter plots.