Noise power spectrum

Download

• Noise Power Spectrum.vi - LabVIEW Virtual Instrument (requires LabVIEW version 2010 or higher)

• Noise Power Spectrum.exe - Stand-alone executable (download folder and run setup.exe to install)

• JavaScript version - runs directly in web browser

Description

A noise power spectrum (NPS) displays the various frequency components that comprise the noise in a time-based signal.  A Fourier transform is performed on the signal to convert it from the time domain to the frequency domain.  The NPS then shows the mean-square noise per unit frequency interval versus the frequency. 

In this simulation background noise is simulated by adding together two sine waves with user-defined frequencies, amplitudes, and phase difference, along with Gaussian white noise.  The power spectrum is calculated and both the time-based signal and the NPS are displayed.

(Reference: Ingle and Crouch, Spectrochemical Analysis, Prentice-Hall 1988)

Front panel

Guiding questions

1. 1. Make a sketch of the power spectrum that results from using the following combination of sine waves with no added noise:  #1 – frequency = 10, amplitude = 2; #2 – frequency = 50, amplitude = 3, phase = 0.

   2. Now add noise with a standard deviation of 8.  Sketch the new power spectrum.  What does this change in the power spectrum say about the frequencies of the noise?

   3. What effect does changing the phase separation have on the time-base signal?  What effect does this have on the power spectrum?