It is particularly important to select a window that is long enough that it allows the DUT waveforms to completely settle to its steady state DC level. We are about to start making high-frequency analysis of the DUT, and we need to allow the signal to settle to make this analysis accurately.
We also need to make sure that a sufficient number of data points is selected in the oscilloscope acquisition window. This is particularly critical for analyzing long interconnects, such as cables. The sample interval should be at most one third the risetime of the clock signal you will be using to generate your eye. In the S(f) tab, the S-parameter frequency should be displayed to at least 1.5/ tr, where tr is the risetime of the clock signal you will use to generate your eye. The highest displayed frequency ( fupper) is related to the time domain time step ( tstep), window length ( twindow) and the number of points ( N) as shown in this equation:
This FAQ Applies to:
Product: CSA8000B, CSA8000, TDS8000, TDS8000B, CSA8200, TDS8200, 80SICON, 80SSPAR, 80SICMX
FAQ ID : 55356View all FAQs »