A New Smart Antenna for CDMA using Nelder-Mead Simplex Algorithm and ESPAR Antenna

This paper proposes a new smart antenna for CDMA using Nelder-Mead (NM) simplex algorithm and a new structure different from the uniform linear array. This smart antenna consists of an active element in the center of a circle having a number of passive elements with variable reactances on its peripheral (it is called an electronically steerable passive array radiator or ESPAR). The proposed smart antenna uses the Nelder-Mead simplex algorithm to adapt its pattern by updating the values of the reactances, as well as to adapt weight vector, which is used for weighting the signals received by different elements of the antenna. For performance comparison the cost function improvement and the pattern of this smart antenna is compared with that of the same ESPAR antenna using the steepest descent algorithm. Simulation results show that by using NM algorithm the length of training sequence required for channel estimation is reduced. This is very important in real-time adaptation systems