Output Power Measurement on Noise Sources

Noise sources used for noise figure and gain measurements are typically controlled by the spectrum analyzer or noise figure meter instruments and are calibrated with their ENR value (Excess noise ratio). While this external control and the use of ENR values is common in noise figure test, it may be difficult in system applications where the noise source control is not available, and the use of ENR values is replaced with the values for the noise output power of the noise source. The calculation of the output power for the noise source requires to know the P_hot value (hot power) which is not a common specification for noise sources used in test and measurement applications.

This application note describes a technique to perform a calibrated noise power measurement (P_hot) with spectrum analyzers and noise sources. The next sections will give further details.