On optimum impedance pattern for accurate wideband noise parameter characterization

At least four source impedances are required to characterize the noise parameters of a two‐port network. The accuracy of the noise parameters depends on the configuration of the employed source impedances (pattern). The configuration of a specified pattern, generated generally by an impedance tuner, changes with frequency, and as such, the accuracy is usually degraded in a wideband characterization. To realize a low‐error wideband noise characterization, the present article thoroughly investigates the method of choosing a four‐source impedance pattern. A Monte Carlo simulation‐based approach is proposed to obtain the desired impedance patterns. The measurement and simulation results show that the noise parameters are accurately extracted when an impedance pattern is configured by a source impedance located near the center of the Smith chart and three other impedances located as close to the edge as possible with interphase separations of at least 45°. While the interphase separations remain unchanged, the impedance pattern rotation around the center of the Smith chart does not affect the accuracy of the extracted noise parameters, as demonstrated analytically here. The resultant impedance pattern realizes a wideband characterization from f0 to 3.5f0 without using an impedance tuner. The obtained accuracy is comparable to methods employing a redundant number of source impedances.