The power spectral density (PSD) of a signal describes the distribution of power into the frequency components, which compose the resulting signal. Power spectral density is commonly expressed in watts per hertz (W/Hz).In signal processing, a periodogram is an estimate of the spectral density of a signal. The term was coined by Arthur Schuster, the periodogram is a component of more sophisticated methods. It is the most common tool for examining the amplitude vs frequency characteristics of FIR filters and window functions. FFT spectrum analyzers are also implemented as a time-sequence of periodograms.
Students can experiment on amplitude vs frequency characteristics, windows functions or FFT spectrum analysis with the help of the FreeScopes User Interface and SkyRadar's various radars.