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One of the limitations of discrete-time sampling is an effect called aliasing. ... Undersampling is essentially sampling too slowly, or sampling at a rate below the Nyquist frequency for a particular signal of interest. Undersampling leads to aliasing and the original signal cannot be properly reconstructed.
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zone.ni.com/devzone/cda/tut/p/id/3000
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The Nyquist Sampling Theorem states that to avoid aliasing occuring in the sampling of a signal the samping rate should be greater than or equal to twice the highest frequency present in the signal. This is refered to as the Nyquist sampling rate.
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www.cage.curtin.edu.au/mechanical/info/vibrations/tut3....
www.cage.curtin.edu.au/mechanical/info/vibrations/tut3.htm
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Notice that if you leave all the components in the original signal and select a low sampling frequency, aliasing will occur. This aliasing will result in the reconstructed signal not matching the original signal. However, you can try to limit the amount of aliasing by filtering out the higher frequencies in the signal.
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www2.egr.uh.edu/~glover/applets/Sampling/Sampling.html
www2.egr.uh.edu/~glover/applets/Sampling/Sampling.html
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Understanding Aliasing, Sampling Rate and the Use of Power Spectral Densities ... Aliasing is the misinterpretation of high frequencies (above half of the sampling frequency) as lower frequencies. This is a problem that must be avoided when digitizing continuous signals.
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www-gateway.vpr.drexel.edu/files/bioengg_Instrumentatio...
www-gateway.vpr.drexel.edu/files/bioengg_Instrumentation/site/Review/Aliasing.html
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Demonstration of Aliasing of a Sinusoidal Signal ... According to the sampling theorem, a sinusoidal signal (or component of a more complex signal) can be correctly reconstructed from values sampled at discrete, uniform intervals as long as the signal frequency is less than half the sampling frequency.
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www.dsptutor.freeuk.com/aliasing/AD102.html
www.dsptutor.freeuk.com/aliasing/AD102.html
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To avoid aliasing, you must preserve the following condition: 1/T ≥ 2α, or 1/T ≥ 2BW. This result can be expressed in terms of the sampling frequency: Thus, the minimum sampling frequency necessary for sampling without aliasing is 2BW. This result is generally known as the Nyquist criterion.
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www.maxim-ic.com/appnotes.cfm/an_pk/3628
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Point sampling in the spatial domain corresponds to the point by point multiplication of a sampling impulse function times the analog signal to be sampled. ... Look at examples of point sampling without and with aliasing:
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www.siggraph.org/education/materials/HyperGraph/aliasin...
www.siggraph.org/education/materials/HyperGraph/aliasing/alias3.htm
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Cutoff frequency for anti-aliasing LP filter.; Example: Suppose there is noise at all frequencies (white noise), but that your signal has information only below 1000 Hz. What would be a reasonable sampling rate and what should be the cutoff frequency for the anti-aliasing filter?
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www.engin.brown.edu/courses/en123/Lectures/SampThm03.ht...
www.engin.brown.edu/courses/en123/Lectures/SampThm03.htm
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