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A spectrum analyzer is a device used to examine the spectral composition of some electrical, acoustic, or optical waveform.
Often, it measures the power spectrum.
There are analogue and digital spectrum analyzers:
An analogue spectrum analyzer uses either a variable bandpass filter whose mid-frequency is automatically tuned (shifted, swept) through the range of frequencies of which the spectrum is to be measured or a superheterodyne receiver where the local oscillator is swept through a range of frequencies.
A digital spectrum analyzer uses the Fast Fourier transform (FFT), a mathematical process that transforms a waveform into the components of its frequency spectrum. As a result, computer programs can compute such transforms, and makes audio processing easier. FFTs have applications in much wider fields.
Some spectrum analyzers (such as Tektronix's family of "real-time spectrum analyzers") use a hybrid technique where the incoming signal is first down-converted to a lower frequency using superheterodyne techniques and then analyzed using FFT techniques.
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See also
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Non-electronic spectrum analyzers
Used to measure atomic particles.
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