Theory of coupled folded antennas

Formulas for the mutual and self-impedance of two identical nonstaggered parallel-folded dipoles are developed. A generalization of the theory permits determination of these impedances for any identical dual configuration of wires, no matter how complicated, provided the structures are symmetrical with respect to the driving points. If the impedance of any single-conductor solid-wire element in a symmetrical circular array of linear radiators is known, the impedance of each element in a similar array consisting of folded-wire structures is readily obtained. Two obvious practical uses of the theory are: 1) the determination of the performance of a two-element folded antenna array, when one antenna is a tuned parasite, functioning as a director or reflector; and 2) determination of the driving-point impedance of a folded antenna parallel to a highly-conducting plane.