Quasi-ideal multilayer two- and three-strip directional couplers for monolithic and hybrid MICs

In this paper, the properties of multilayer two- and three-strip asymmetric coupled lines are described using their coupled-mode parameters. Examples of quasi-ideal, microstrip, and coplanar directional couplers designed in monolithic and hybrid microwave integrated-circuit technology, consisting of various layered structures of bilevel and trilevel coupled lines, are presented together with experimental results for two 3-dB couplers on ceramic-filled polytetrafluoroethylene and polyimide laminates.