Virtually every engineer is familiar with the Heisenberg uncertainty principle, which states that you can't know an electron's position and momentum simultaneously. You might not realize, though, that a similar principle comes into play for one of the most familiar DSP techniques, the FFT. As this article shows, you can either know everything about a signal in the time domain but with zero frequency-domain resolution, or have complete frequency information about a signal and no time-domain resolution, or a situation that falls somewhere in between. Because of this fact, the FFT sometimes fails to provide necessary information in certain applications. This column introduces a new and potentially useful replacement that solves some of the FFT's problems -- wavelets. Wavelets have attracted considerable attention lately, and this article discusses what they actually are and what they can do.

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