Six-Port Reflectometer Based on Modified Hybrid Couplers

Six-port reflectometers have traditionally employed hybrid couplers as their building blocks, but the instruments reported thus far in the literature do not comply with the optimum design specifications. This paper describes a six-port reflectometer based on four-port coplanar-waveguide couplers that have been modified so as to meet such design requirements. Additional design parameters have been incorporated so that adjustments may be made to correct for residual hardware imperfections. Laboratory tests have confirmed an operating bandwidth of 90% (from 1.1 to 2.9 GHz) for the resulting reflectometer.