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Frequency Alias and Sample Principle

When transform a analog signal to digital signal, the sample frequency must large then twice the maxium frequency of the signal. This is called sample principle.
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For example, If you sample a 1100Hz sine wave with 2000Hz, you will get a 100Hz sine wave. This is not true, it is a error of frequency alias.

The applet is used to show the frequency alias error in sampling.It can produces different sine signals and sample them at a fixed sampled rate(5120Hz).

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Frequency Alias and Sample Principle
Usage:
1.Input Frequency, Amplitude and phase of a sine signal.
2.Press "Generate" to sample this signal, Locate the frequency of sampled signal, 
Compare with original signal, and explain it by sample principle.
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