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Variable Phenomena Nyquist Sampling Harry Nyquist (1889 – 1976) • Consider a sine wave. • How often do we need to sample it in order to figure out its frequency? If we sample with a frequency which corresponds to once per wavelength, we would think the sine wave is constant If we sample 1.5 times the real frequency, we’d think the function is a sine with a longer wavelength (the red curve) If we sample at twice the real frequency, we get the right answer Nyquist Sampling: For lossless digitization, sample at at least twice the frequency.