Amplitude accuracy in the presence of noise

This paper addresses amplitude measurement accuracy near the system noise floor by first defining the maximum theoretical S/N available for measuring a signal at a regulatory limit, and then showing how this ratio is reduced by the physical limitations of the components of the measurement system. Shown next is a quantization of the magnitude of the errors when measuring CW signals in a background of broadband noise as a function of the type of detection used. Next, the paper discusses and quantifies the relationship between the input S/N ratio and the detected S/N ratio that is seen on the measuring instrument. The paper closes with a discussion of a method by which a designer can determine the maximum cable loss allowable to guarantee a specific S/N ratio when using known antennas and measuring instruments.