Mutual coupling between orthogonal electrically small dipole antennas

Abstract

In some applications, it may be desirable and/or necessary to closely locate (spacing <<λ) multiple electrically small antennas. In an effort to reduce mutual coupling, small antennas are often oriented such that their isolated far-electric and magnetic fields are orthogonal. In this paper, we examine the mutual coupling between co-located and closely spaced orthogonal small dipole antennas. We illustrate that if small regions of the dipoles are not orthogonal, particularly near their feedpoints, the mutual coupling can be very high and under appropriate load conditions can approach 0 dB. We illustrate how the mutual coupling between the dipoles varies as a function of the dipoles' electrical size and load impedance. Finally, we show that making the electrically small dipoles self-resonant significantly reduces or eliminates the mutual coupling between them.