Aliasyne: Nyquist Sampling Aliasing
Optics, Waves & Sound arc, page 124 of 193. Back to The Pixelated Physics Universe
Who they are
Aliasyne has one line, and says it often: “Sampled too slowly. all of it aliased.”
Aliasyne is a character of the Optics, Waves & Sound arc: drawn in pixels, ruled by one piece of real physics, and never allowed to break it.
The physics
Sampling theorem: a signal must be sampled above twice its highest frequency; below that, frequencies alias.
$$ \begin{gathered} f_s > 2 f_{\max} \end{gathered} $$
| Symbol | Meaning | SI unit |
|---|---|---|
| $f_s$ | sampling frequency | Hz |
| $f_{\max}$ | highest frequency in the signal | Hz |
Sources
Crossovers
Aliasyne meets Phaselocke (Lock-In Amplifier). Aliasyne warns that sampling below twice the highest frequency folds signals into false ones. Phaselocke's lock-in depends on careful filtering that keeps unwanted frequencies out of the band.
Aliasyne meets Siderelle (Sidereal Day). Siderelle's stars rise about 4 minutes earlier each solar day. Aliasyne sees a kind of aliasing in that: sampling the sky once a solar day makes the stars seem to drift slowly westward.
Aliasyne meets Chronolith (Discrete Time Crystal). Chronolith is driven at period T and answers at 2T. Aliasyne points out that sampling her exactly once per drive period would show her flipping every sample, which is just the signature an experiment looks for. Sample more slowly and the rhythm can alias into something false.
Wear the lore
Concept keywords: Nyquist Sampling Aliasing, Aliasyne, Optics, Waves & Sound, physics lore, Pixelated Physics