Thermal White Noise - Johnson–Nyquist noise

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SUMMARY

The discussion centers on measuring thermal white noise, specifically Johnson–Nyquist noise, generated by chemical batteries. Participants debate the correct formulas to use, emphasizing that classical thermodynamics leads to a power spectral density independent of frequency, while quantum effects introduce frequency dependency. The conversation highlights the importance of using the correct equations, particularly the one derived from Nyquist's work, which is applicable at low frequencies. The complexities of calculating frequency in relation to thermal noise and the implications of using the wrong formula are also addressed.

PREREQUISITES
  • Understanding of Johnson–Nyquist noise and its derivation from classical thermodynamics.
  • Familiarity with the concept of power spectral density and its measurement.
  • Knowledge of quantum effects in thermal noise calculations.
  • Basic grasp of complex frequency and its implications in signal processing.
NEXT STEPS
  • Study the derivation of Johnson–Nyquist noise from classical thermodynamics.
  • Learn about the application of the Lambert W equation in solving complex frequency problems.
  • Research the differences between classical and quantum approaches to thermal noise.
  • Examine the role of measurement bandwidth in noise analysis, particularly in low-frequency applications.
USEFUL FOR

Electrical engineers, physicists, and researchers involved in noise measurement and analysis in electronic systems, particularly those working with thermal noise in batteries and low-noise RF applications.

  • #61
Mechatron said:
This problem really hertz

:smile:
 
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  • #62
New theory:

The flicker noise is carried on the 20 kHz signal, so the signal is a carrier signal. In addition to try to calculate the cut off frequency of the flicker noise. From a different think-outside-the-box perspective;
If you can calculate the noise voltage using Johnson's equation for every instance (a unit of time):
If the noise voltage is 0 at 0 ms, 1 V at 250 ms, 0 V at 500 ms, -1 V at 750 ms and 0 V at 1000 ms, don't you agree that the frequency is 1 Hz? So since the thermal radiation generate random noise and generate a noise voltage, and the noise voltage vary, then we can say that the thermal radiation actually does have a frequency on the carrier signal.
 
  • #63
Mechatron said:
If you can calculate the noise voltage using Johnson's equation for every instance (a unit of time)

You can't calculate the noise voltages, it is a random function. It would be like calculating ahead of time rolls of a dice.

Mechatron said:
If the noise voltage is 0 at 0 ms, 1 V at 250 ms, 0 V at 500 ms, -1 V at 750 ms and 0 V at 1000 ms, don't you agree that the frequency is 1 Hz?

No. Because maybe the voltage at 100ms was 4V, and at 101ms was -6V etc. Get it?

Or maybe yes if for this one particular second this random noise voltage just happened to trace out a sine wave.

How likely would you expect this to be?
 
  • #64
Thread locked for technical Moderation
 

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