Quadrature directional couplers using multisection coupled lines

New structure and design methods of directional couplers that can achieve both loose coupling and tight coupling by use of multisection coupled lines are presented. Output voltage formulas at each port are derived from the coupled-line theory. Measured results agree very well with predicted ones. Since the proposed couplers are very small in size and have suitable shape for high-density integrated circuits, they have potential applications in portable terminals for mobile communication systems.