Monopole Design for Superdirectivity with Pattern Radiation Reconfigurable

Abstract

This paper presents a global study for superdirectivity of an array of 2 monopoles antennas. It is principally based on Uzkov’s theory, who define the possibility to obtain a high directivity in order of $N^{2}$ in a desired direction by linearly associating a large number N of radiators closely spaced. A first study is made by exciting monopoles by specific currents excitation in magnitude and phase to obtain a superdirectivity reconfigurable in a desired direction. Secondly, to reduce until eliminate mutual coupling between monopoles, we excite one of monopole by a & [1]. However, the most significant works for a large number of associating radiators is from I.Uzkov [2], who states in 1946 the possibility to make a superdirectivity, meaning a directivity in order of $N^{2}$, by linearly associating a larger number N of closely spaced radiating elements. Then, he showed from equations (1) and (2) defined below that this directivity can be in a desired direction $(\theta ,\varphi )$ when radiating elements are properly excited. unit current and loaded the other one by an impedance determined from uzkov’s theory. Simulator Ansys HFSS is used to calculated impedance matrix $H_{mn}$ of monopoles antennas array and then currents excitation coefficients $a_{{0} {n}}$ used after to determine impedance $Z_{load}$. Simulations show approximately similar results in the 2 cases with a reconfigurable directivity a least in around of $8 . 5 dB$ in a desired direction.