# Variable Phenomena Nyquist Sampling - PowerPoint PPT Presentation

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## Variable Phenomena Nyquist Sampling

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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? – PowerPoint PPT presentation

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Title: Variable Phenomena Nyquist Sampling

1
Variable Phenomena Nyquist Sampling
Harry Nyquist (1889 1976)
2
• Consider a sine wave.
• How often do we need to sample it in order to
figure out its frequency?

3
• If we sample with a frequency which corresponds
to once per wavelength, we would think the sine
wave is constant

4
If we sample 1.5 times the real frequency, wed
think the function is a sine with a longer
wavelength (the red curve)
5
• If we sample at twice the real frequency, we get

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(No Transcript)
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• Nyquist Sampling
• For lossless digitization, sample at at least
twice the frequency.

8
Light curves of Variable Stars
Take Fourier Transform ? Period
9
Phase Plot
Phase, in units of cycles