Noise

Model noise using current or voltage noise source in RF systems

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Libraries:
RF Blockset / Circuit Envelope / Sources

Description

Use the Noise block to model noise as an ideal current or voltage source for blocks. Using this block you can select the noise distribution type as white, piecewise-linear, or colored. When you use a Noise block to simulate noise in an RF model, select the Simulate noise check box in the Configuration block. Otherwise, the model simulates without noise. The Noise block does not depend on the Temperature parameter in the Configuration.

Noise block mask icons are dynamic and show the current type of source. This table shows you how the icons on this block vary based on the type of source you set on the Source type parameter on the block.

Source type: Ideal voltage	Source type: Ideal current

Examples

Explicitly Simulate Resistor Thermal Noise

Use the Noise block to calculate the classic thermal noise floor, kT, for a matched resistor circuit. Model configuration is as follows:

• Open Script

Parameters

Source type — Noise type

Ideal voltage (default) | Ideal current

Noise type, specified as Ideal voltage or Ideal current.

Noise distribution — Noise distribution type

White (default) | Piece-wise linear | Colored

Noise distribution type, specified as White, Piece-wise linear, or Colored.

Noise power spectral density — Single-sided noise power spectral distribution

0 (default) | scalar | vector

Single-sided noise power spectral distribution (PSD), specified as a scalar or vector in V²/Hz or A²/Hz. The single-sided PSD varies based on the noise distribution type. When you set the Noise distribution parameter to one of these options:

• White — Specify the Noise power spectral density parameter as a nonnegative scalar. The noise PSD of white noise is constant across all frequencies and the noise power depends on the bandwidth of the carrier or the time step. This is an uncorrelated noise source.

• Piece-wise linear — Specify the Noise power spectral density parameter as a vector. The vector must be of the same length as the vector you specify in the Frequencies parameter.

  For each carrier, the noise source behaves like a white noise source. The noise PSD of the noise source depends on the carrier, and you can calculate it by performing the linear interpolation at the carrier frequency on the noise spectral density curve.

  The noise spectral density curve represents the variation in noise PSD with respect to frequency. The block uses the values that you specify in the Noise power spectral density and Frequencies parameters to determine this curve.

• Colored — Specify the Noise power spectral density parameter as a vector. The vector must be of the same length as the vector you specify in the Frequencies parameter. This is a correlated noise source.

  The noise spectral density over the bandwidth at the carrier frequency is determined by the noise spectral density curve unless you set the Impulse response duration parameter to 0.

The units of the single-sided PSD depend on the Source type parameter. When you set the Source type parameter to:

• Ideal voltage — The block simulates the PSD in V²/Hz.

• Ideal Current — The block simulates the PSD in A²/Hz.

Frequencies — Frequencies for piece-wise linear noise distribution

0 Hz (default) | vector of non-negative frequencies | Hz | kHz | MHz | GHz

Frequencies for piece-wise linear noise distribution, specified as vector of non-negative frequencies.

Automatically estimate impulse response duration — Estimate impulse response duration

on (default) | off

Select this parameter for the block to automatically estimate impulse response duration or clear this parameter to specify the impulse response duration using the Impulse response duration parameter..

Dependencies

To enable this parameter, set Noise Distribution to Colored.

Impulse response duration — Impulse response duration to simulate colored noise

1e-10 s (default) | scalar | s | ms | us | ns

Impulse response duration to simulate colored noise, specified as a scalar in s, ms, us, or ns. When you set the Impulse response duration parameter to 0, the software interpolates linearly as with a Piece-wise linear noise source.

Dependencies

To enable this parameter, set Noise Distribution to Colored and clear Automatically estimate impulse response duration.

Ground and hide negative terminals — Ground RF circuit terminals

on (default) | off

Select this option to internally ground and hide the negative terminals. To expose the negative terminals, clear the option. By exposing these terminals, you can connect them to other parts of your model.

By default, this option is selected.

Version History

Introduced in R2010b

R2021b: Noise block icon updated

Starting in R2021b, the Noise block icon is now updated. When you open a model created before R2021b containing a Noise block, the software replaces the block icon with the R2021b version.