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About FFT Spectrum Analyzers
Application Note #1
What is an FFT Spectrum Analyzer? frequency points as there are time points. (Remember
Nyquist's theorem.) Suppose that you take 1024 samples at
FFT Spectrum Analyzers, such as the SR760, SR770, SR780 256 kHz. It takes 4 ms to take this time record. The FFT of this
and SR785, take a time varying input signal, like you would record yields 512 frequency pointsbut over what frequency
see on an oscilloscope trace, and compute its frequency spectrum. range? The highest frequency will be determined by the period
of two time samples or 128 kHz. The lowest frequency is just
Fourier's theorem states that any waveform in the time domain the period of the entire record or 1/(4 ms) or 250 Hz.
can be represented by the weighted sum of s |