Six-port reflectometer theory for symmetrical five-port junction with directional coupler

In the ideal case, a symmetrical five-port junction, together with a directional coupler, forms one of those few six-port networks that satisfy the criteria for optimum six-port reflectometer performance. Imperfections however exist in the actual hardware, and they degrade the performance of this otherwise ideal circuit. Although the six-port technique accounts for these imperfections globally in the calibration procedure, it is nevertheless important that a proper analysis of how the system degradations arise be made. The paper provides such a theoretical study. In the course of the investigations, it was found that improvements in the performance of the hardware circuit may be obtained simply by re-arranging the inter-connections among the constituent components.