Undersampling and Clock Source Sensitivity: Impact on SNR

The clock source becomes more critical when undersampling, as the sensitivity to clock jitter or phase noise increases with higher input frequencies. For instance, a clock source that reduces the signal-to-noise ratio (SNR) of a full-scale signal by 1dB at 70MHz will decrease SNR by 3dB at 140MHz and 4.5dB at 190MHz.