Four-port reflectometer design and implementation

The concept of six-port reflectometer theory was first introduced by Hoer and Engen (G. F. Engen and C.A. Hoer, IEEE Trans., Inst. and Meas., vol-21, no. 4, pp.470-474, 1972) and then became an attractive method for measurement of voltage, current, impedance, phase and power. Five port reflectometers have also been investigated for complex reflection coefficient measurement. Although six-port and five port reflectometers are attractive and low cost alternatives to network analyzers, it is not convenient to use them in practice since commercially available devices are mainly four port directional couplers.