On the Use of Characteristic Mode Analysis for Dual Beam Antenna Array

This paper presents a design of probe fed dual beam 2x2 antenna array at 2.4 GHz. The dual beam of the antenna array was obtained by a simple technique of exciting the neighboring elements with phases of 180°. The characteristic mode analysis(CMA) was performed to get the better understanding of multiport structure. The critical parameters of CMA, such as modal currents, modal radiation patterns, modal significance, and modal weighting coefficient, were used to reveal the physical insight behind the dual beam behavior. It showed how the feed-induced phase reversal affects the surface currents to produce a dual beam. The dual beam was produced at the angle of 55° with a beamwidth of 61° and a peak gain of 8 dB. The antenna array showed stable gain with a cross-polarization level as low as -60 dB. The antenna elements were placed at a distance of 0.45λ from each other.