White Noise

SD Toolbox Reference

White Noise

Models a noise source with white power spectral density.

Library

SD Toolbox.

Description

The White Noise block models a noise source with white power spectral density.

A white noise source can be modeled with a Gaussian random process featuring a standard deviation V_n which represents also the RMS value of the noise (i.e. the square root of the noise power V_n²).

The noise power V_n² can be evaluated through a transistor-level noise simulation of the complete Switched-Capacitor (SC) circuit considered (e.g. the integrator of a Sigma-Delta modulator) in the proper clock phase, including feedback, sampling and load capacitors. The resulting output referred noise power spectral density has to be integrated over the whole frequency spectrum, eventually taking into account the degradation of the thermal noise power-spectral density introduced by the auto-zero or correlated double sampling techniques. If 1/f noise is important it is preferrable to use the Colored Noise block.

In this model we consider only the contribution of the sampled noise, assuming that no continuous-time paths are present across the Sigma-Delta modulator (this is typically the case in SC Sigma-Delta modulators due to the presence of a latched quantizer).

Parameters

• Sample Time: Period of the sampling signal in s (T_s = 1/f_s, where f_s is the sampling frequency)
• Noise Standard Deviation: Standard deviation of the noise in V
• Random Number Seed: Seed for the random number generator; different seeds among different blocks using the random number generator guarantee that the random sequences are uncorrelated

Colored Noise

KT/C Noise