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Is there a 'Nyquist Criteria' for the minimum samples per chip that are needed for a correlator? I've heard 2, but will 1 work? What are the implications of having less than the minimum (in the context of radar and communications)?

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  • $\begingroup$ What exactly is this samples per chip quantity you're taking about? What is a chip? $\endgroup$ – Phonon May 23 '14 at 0:15
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    $\begingroup$ @Phonon I believe that he is referring to DSSS chips. $\endgroup$ – Jim Clay May 23 '14 at 0:30
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Actually much less than 1 sample/chip will work for DSSS. Doing so erodes the spreading gain and makes chip level detection impractical, but it works. The undersampled spreading sequence simply acts as a vector (subspace) for the undersampled signal. Matched filtering is still matched filtering -- as long as you are still sampled well above the symbol (not chip) rate.

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It is not a good idea to do 1 sample/chip because if you happen to have the samples at the chip transitions then demodulation will go poorly. Also, if you have much carrier offset you will likely lose and/or alias part of the signal.

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