What's Your Sine?

摘要

Instruments such as frequency meters, voltmeters, and amme-ters provide some information about a signal, but when the signal varies with time, measurements get more complicated. Analysis of a continuously varying signal, such as a sine wave, requires sampling it at discrete times spaced at uniform intervals. The sampling produces an array of values software can process to extract information about frequency content and relative power levels. Most signal analyses rely on the Fourier transform, a mathematical tool that transforms a continuous signal from the time domain into the frequency domain. But engineers must work with discrete-value discrete-time data, rather than continuous analog signals, so they employ a fast Fourier transform (FFT). An FFT algorithm produces a plot of spectral power vs. frequency, so a pure 1 -kHz sine wave, for example, will produce a single peak at 1 kHz.