Reactively matched long slot linear connected array antenna

A linear three-element slot antenna array with intentionally strong mutual coupling between the elements, a so-called connected array, is presented. By simultaneously feeding all three ports of the array, at different frequencies over an octave bandwidth and with different phases, feed-port reflection coefficients with magnitude larger than one, or negative active feed impedances, can occur. A reactive pre-match is proposed to avoid these particular cases and entirely passive impedance transformation to 50 Ohm feed impedance becomes possible. This concept is illustrated by experiments with a radiating slot of a length of 40% of a wavelength at 1.7 GHz, with three equidistant feeds, operating with in-phase feed signals at 1.7 GHz, 2.55 GHz and 3.4 GHz, respectively, as well as with phase-increment feed for beam steering at 1.7 GHz. Beam steering towards 30 degrees off broadside at 1.7 GHz is demonstrated from this slot.