Impossibility of Linear Two-Port Noise-Parameter Measurement with a Single Temperature Noise Source

The noise parameters of a linear two-port are usually evaluated through four measurements of the noise figure of the two-port, and the noise figure is in turn determined through the measurements of the noise power output of the two-port when a noise source is connected at its input. It is shown that if the noise power output is the only measured quantity, then the noise parameters cannot be calculated from measurements carried out with a single value of the source noise temperature. The minimum requirements for the determination of noise parameters are established.