Noise source
A noise source gives white noise of a set density up to a set bandwidth. Add it to a signal to see how a filter, a lock-in or a comparator copes with it.
Ports
One output, out.
The model
Its output is noise alone, a one-sided power spectral density flat up to the bandwidth \(B\) and zero above:
\[S(f) = e_n^2 \quad (f \le B), \qquad v_\text{rms} = e_n\sqrt{B},\]with \(e_n\) the density in nV/√Hz. Noise is kept as a density through the network (see Electronics: signals): a filter shapes it by \(\vert H(f)\vert^2\), and a mixer moves it about the other input’s tones.
Settings
| Field | Default | Meaning |
|---|---|---|
psd | 100 | Density (nV/√Hz) |
bw | 1000000 | Bandwidth (Hz) |
From the tool's own tables, file format version 1: the names are those in a .jekray file.
Readouts
The panel gives its output in the steady state: the DC level, the five strongest tones (each one’s amplitude, rms and the phase of its cosine), and the noise, as a density at 1 kHz and in rms from 1 Hz to 1 GHz. Any notes, such as an input left unwired or an output past its limit, are listed under it.
Assumptions
- The noise is Gaussian, white and stationary, with a sharp edge at its bandwidth.
- Noise from one source that reaches a block by two paths is added as if the two were unrelated.
Related
- Summing junction, to add it to a signal.
- Spectrum analyser.