# Check temperature, noise bandwidth and sample time in JoSIM®-Pro

Distinguish thermal-noise settings from an explicit NOISE waveform and from temperature-dependent junction model parameters.

## Compatibility

2.9.0 release target; review-build/source evidence

Published guidance with release-applicability limits. Confirm package applicability before following this guide.

## Thermal-noise settings

The maintained syntax uses .TEMP for temperature in kelvin and .NEB for effective noise bandwidth in hertz. Supported devices may override the global settings with temp= and neb=.

Enter a temperature such as 77 kelvin as .TEMP 77. Do not append the engineering suffix K expecting a kelvin unit: in numeric expressions it can mean a factor of one thousand.

```text
.TEMP 4.2
.NEB 1GHz
R1 1 0 50 temp=4.2 neb=1GHz
```

## Explicit noise waveform

NOISE(A [Td [Ts]]) takes a spectral amplitude, start delay and sample time; the documented default sample time is Tstep. This is a separate interface from .TEMP/.NEB.

Keep simulation timestep, noise sampling and measurement/averaging windows explicit when comparing runs. Account for random realisations and settling; a different trace is not alone evidence of changed noise power.

## Avoid a universal conversion formula

Historical correspondence corrected earlier bandwidth/sample-time advice. This draft intentionally does not supply one conversion between effective thermal bandwidth and an arbitrary explicit sampled-noise source. Verify the intended noise definition and current implementation before quantitative comparisons.

Junction model T/TC parameters can also change device behaviour; that is separate from adding thermal-noise excitation.

## Sources and verification details

Recorded inputs/builds only. Complete walkthrough and final-package acceptance remain separate.



- support:SUP-014: Generalised editorial finding; outcome qualification retained
- support:SUP-015: Generalised editorial finding; outcome qualification retained
- josim-pro:docs/manual_source/sections/syntax.tex: Noise; noise settings; Josephson junction parameters
- owner:technical-review-20261102: JoSIM-Pro 2.9 chosen as the public starting path; release availability must be checked before publication

- Temperature suffix and quantitative noise behaviour still need a fresh controlled walkthrough. Historical formula corrections are not numerical validation of this draft.
- The owner accepted the modelling explanation on 2 November 2026. Applicable release/platform and unrecorded walkthrough checks remain pending.

## Related guides

- [RN, R0 and temperature give unexpected junction resistance](/knowledge-base/josim-junction-resistance)
- [Coupled inductors cause divergence or invalid-matrix errors](/knowledge-base/josim-coupling-validity)