Differentially-fed re-entrant coupled-line directional couplers

Abstract

In this paper differentially-fed directional couplers have been proposed in which two-conductor balanced lines are arranged vertically. The possible realizable coupling in such structures is investigated and a method for coupling enhancement is proposed. The method is based on the re-entrant technique utilized in the design of single ended coupled line directional couplers. The results of theoretical investigation have been confirmed by measurements of two differentially-fed directional couplers having coupling 10 dB and 3 dB.