Matched symmetrical five-port microstrip coupler

Other researchers have fabricated a symmetrical five-port microstrip coupler (with a double-ring structure) yielding a bandwidth of 58%. It has been found in this paper that a simple modification of the design topology allows the coupler's bandwidth to be broadened to 76%. A first-order model of the new prototype has also been developed, and tests have confirmed that close agreement can be expected between the predicted and experimental results for the coupler's scattering coefficients.