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Analyzers designed to measure and display the amplitudes of the sinusoidal components of a signal as a function of frequency (i.e., frequency domain representation or spectrum). These analyzers are electronic instruments that function as a combination of a heterodyne radio receiver, a signal strength meter, and a graphic plotter or display; the display shows the meter reading (amplitude) versus the frequency as the receiver is tuned from one end of the band to the other. Spectrum analyzers may be used to analyze or check the spectrum of bioelectrical or medical device signals and/or to characterize the electromagnetic interference (EMI) coming from other equipment and/or from natural sources (e.g., thunderstorms). Some spectrum analyzers perform real-time spectrum analysis with high accuracy and resolution using digital processing techniques based on the fast Fourier transform (FFT); they are especially useful when low-frequency (e.g., less than 100 kHz) or very fast measurements are needed (e.g., speech analysis).
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