Modifying hybrid coupler design to enhance six-port reflectometer performance

In general, six-port reflectometers based on standard four-port couplers do not satisfy the ideal-case design specifications stipulated for optimum performance. It is shown in the present paper that the design goals can be met by modifying the four-port coupler´s characteristics. Laboratory tests on a prototype six-port reflectometer which employs four modified rat-race couplers have corroborated the validity of such an approach.