Measurement uncertainty analysis and design of a broadband four‐port reflectometer

Abstract

An impact of power distribution provided by the four‐port reflectometer network on the uncertainty of complex reflection coefficient measurements is investigated. As a result, parameters of a four‐port reflectometer with theoretically optimal power distribution that ensures the lowest obtainable measurement uncertainty are determined. In addition, a new four‐port reflectometer that allows for achieving the derived optimal parameters over a wide frequency range is proposed. It also features a simple structure; therefore, low‐cost single‐layer microstrip realisation can be easily obtained. To verify the circuit's performance, a broadband four‐port reflectometer operating in 1–3 GHz frequency range has been designed, manufactured, and used for reflection coefficients’ measurements. The obtained results are in a very good accordance with the reference values provided by measurements performed with a commercial vector network analyser.