Modeling and Design of Symmetrical Six-Port Waveguide Junction for Six-Port Reflectometer Application

Abstract

The Six-Port technique is a well known technique introduced in 1972 by Hoer and Engen. Unlike VNA which uses frequency down conversion to acquire the phase information, the Six-Port technique directly extracts both magnitude and phase of the reflection coefficient with only four scalar power measurements. To achieve the optimum performance of the Six-Port technique, a six-port network that minimizes the effects of imperfections is needed. First, we develop a computer model that is able to predict the scattering coefficients of the symmetrical N-port step waveguide junction. Then, we will perform some numerical experiments. We use this model to search for a new six-port junction design able to satisfy the requirements for the optimum performance. To use the designed six-port network as a reflectometer, we develop a calibration procedure based on an optimization approach. Finally, we measure the reflection coefficients of different DUTs which are in agreement (+/- 0.02 magnitude, +/-2 degree phase) with the results obtained by a VNA (viz. HP8510C).