|
|
If the Nyquist sampling criterion is not met, the effect
is for the sum and difference components associated with each harmonic of the sampling
signal to overlap with those of adjacent harmonics in the sampling spectrum. Clearly it is
now not possible to filter out the wanted from the unwanted signals and thus perfect
reconstruction of the original signal is not achieved. Some modern A/D or D/A converters, called sigma-delta converters, use many-fold oversampling (x64 or x128 is typical) with in-built decimation or interpolation filters. |