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Spectral density

(Redirected from Power spectral density)

In physics, the spectral density, or more correctly the power spectral density (PSD) of a given bandwidth of electromagnetic radiation is the total power in this bandwidth divided by the specified bandwidth.

Spectral density is usually expressed in watts per hertz (W/Hz).

There exist both power and energy spectral densities. The energy spectral density is defined as

$\Psi_x(f) = \left| X(f) \right|^2.$

Note that the total energy in the frequency domain equals the total energy in the time domain:

$\int \left| x(t) \right|^2\, dt = \int \Psi_x(f)\, df.$

This is a result of Parseval's theorem.

Practically, for discrete-time signals, the PSD is calculated using the FFT. One example is Welch's method.

External links

Power Spectral Density Function - from Wolfram Research's "Time Series Documentation"

Categories: Physics

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10-26-2009 08:16:03
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