But, soft-clipping is not going to change periodicity, is it?
So if you soft-clip a sine wave, be it polynomial or not, the outcome is periodical at the same period, so contains only perfect harmonics. It cannot behave in the "folded alias" way one usually suspect.
Xue On 02/11/2013 06:36, robert bristow-johnson wrote:
just to be clear. the general rule is that an Nth-order polynomial can generate images at frequencies up to the Nth multiple of the frequency of the original baseband image. it is sufficient to oversample by a factor of (N+1)/2 to prevent any of these generated images from potentially folding back into the baseband. e.g. 3rd-order softclipping requires upsampling by a factor of 2. another e.g. 7th-order softclipping requires upsampling by a factor of 4 to avoid any folded aliases from contaminating the original baseband.
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