Distributed and Lumped-Element Realizations of Wideband Branch-Line Hybrids with Arbitrary Power Division

Abstract

A two-section branch-line coupler with an arbitrary output power division is realized by lumped and distributed elements. Based on the transmission line theory, as well as the basic circuit theory, transcendental equations are derived and formulated to determine its circuit parameters. For circuit miniaturization, the transmission-line sections are replaced by either a lumped pi-network and realized with lumped capacitors. Several design curves are provided for ease of circuit implementation. Two circuits with output power division ratios vertical bar Delta vertical bar= 3 dB are fabricated and measured.