In order to increase the convergence speed of ESPAR antenna control, a variable step search algorithm is proposed. During Convergence, elemental reactance control voltages are stepped in succession with an examination function determining the effectiveness of each control voltage step. If the examination function improves with the current step, the new control voltage is retained and the current values of step size and direction are passed to the corresponding element's next iteration. Conversely, should the examination function degrade, the step direction is reversed and step size reduced by a factor of q. The algorithm characteristics are shown by investigating the convergence speed's relationship with the initial step size, step reduction factor q and interference direction of arrival.
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