Spectral Analysis

MatDeck has several functions for spectral analysis as well as determining the frequency content of a signal. The following functions are fft-based non-parametric tools: periodogram(), powspectwelch() and spectrogram().

In signal processing, a periodogram is used to estimate the spectral density power of the signal. The periodogram is a standard component in the more complex methods for spectral estimation, such as Welch’s method for spectral estimation. Periodograms are calculated as a Fourier transform of an auto-correlation function that is FT{x(t)*x(-t)}= X(f)*X*(f)=abs(X(f))2. MatDeck contains a function called periodogram().

Welch’s method for estimating the power spectra is carried out by dividing the time signal into successive blocks, forming the periodogram for each block, and then averaging them. MatDeck contains a function, powspectwelch(), specifically designed for this purpose.

A spectrogram is a visual representation of the spectrum of a signal, showing the frequency components as they vary with time. MatDeck contains a function, spectrogram(), which shows the results in a 3D graph.

Spectral analysis examples:

• Periodogram
• Spectrogram
• Welch Method