Noise floor in ADC testing

Noise floor is a frequency spectrum parameter that is widely used in ADC testing although it has not been properly defined and described by a formula in any ADC standards yet. IEEE Std 1057-1994 does not mention the noise floor but it generally uses noise or noise level that is not defined. IEEE Std 12412000 provides a formula for noise floor computation depending on the number of ADC bits; consequently, such noise floor corresponds to that of the ideal ADC and not to the reality. In the last version of DYNAD (version 3.3, Sept. 2000), the definition of the noise floor is the most precise. Harmonic components, gain and offset errors are not considered there when determining the noise floor and a formula for noise floor computation is also provided. Unfortunately, only white noise is used in this standard and spurious components are not considered there. The noise floor is commonly understood as the average (sometimes also maximal) power of random noise (i.e. the noise that is freed of any harmonic, spurious and DC components) in frequency spectrum. It implies that the noise floor determines the detection power level under which no weak signals can be discovered. It also determines power uncertainty of evaluation of any spectral component due to noise. So, the noise floor is important information in frequency domain. Once estimated, it can be used e.g. for the detection of strong spectral components.