The AD9957's datasheet says that encoding and pulse shaping of symbols must be implemented before the data is presented to the input of the AD9957. What if I ignore the pulse shaping operation?
The purpose of pulse shaping is to limit the effective bandwidth of the signal since our sampling rate is finite. We need to ensure that no spectral components exist beyond the nyquist frequency. So if we don't introduce pulse shaping, spurs that exist beyond nyquist might foldback to the zone below nyquist which could negatively affect our sampled signal.
Pulse shaping is not an absolute necessity. It depends on the spectral bandwidth requirements of your particular application. See ADI application note AN-922 for a detailed description of pulse shaping.
Yes, pulse shaping is not very necessary. But for AD9957, it seems necessary. I have tried that the pseudo-random noise code which was sent to the input of AD9957, was not pulse-shaped, but the result was wrong.
Thanks very much!
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