Re: Is higher oversampling ratio better in signal fidelity in digital world?

Jon Harris wrote:

"Thomas Magma" <somewhere@xxxxxxxxxxxxxxxxxx> wrote in message
news:E0obg.175306$P01.14809@xxxxxxxxxxx


Thinking in the time domain, as you lower the sample rate you increase the
digitization (Your sampled sine wave will start to look like a square wave).
Clocking that data through a DAC at the same rate will produce strong
harmonics (3rd 5th 7th etc). You can't regenerate the original sine wave out
of a DAC no matter what digital reconstruction filtering you use if the
playback rate is too slow. The output of a DAC will always start digitizing
and producing harmonics as you lower the sample/playback rate, unless you have
exceeded the full power bandwidth of the DAC or have analog filtering after
the DAC.


A perfect analog reconstruction filter, i.e. brickwall at 100 Hz _would_
perfectly reconstruct the original sine wave with no "harmonics" as you call
them or aliases.

Not really. The real (cosine) component can be reconstructed, but the
imaginary (sine) component will always be unknown. It will take a very
long time to learn the imaginary component if the sampled frequency is
only very slightly less than 100 Hz.

Such a filter can't be built, hence it is useful to oversample
by some amount and/or use digital resampling filters to help.

Jerry
--
Engineering is the art of making what you want from things you can get.
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