From: Daniel, Erik S. (Daniel.Erik@mayo.edu)
Date: Thu May 11 2000 - 05:14:34 PDT
> Second, yes thanks for giving me a chance to pick up on the
> subject of
> TDR. As you explain there are two primary methods one using
> two opposing pulses
> and the other using a single pulse to drive each line in turn and
> calculating the
> resultant differential impedance.
Can you provide more information on how exactly your instrument measures the
single-ended responses and subsequently computes the odd and even mode
impedances? Specifically, when you pulse line 1 and observe its response,
what is done with line 2? Is it grounded? Open? Terminated in 50 Ohms?
If it is terminated, is the voltage at this terminal sampled as well as the
voltage on line 1? What mathematics is then used to compute even and odd
impedances? It seems that with this type of measurement it is still
critical to ensure that identical pulse delay and pulse shape is used to
stimulate each of the lines independently -- what steps are taken to ensure
this is the case?
> There are advantages and disadvantages to both methods but we have
> done extensive testing on thousands of coupons and correlated
> results from
> both types of systems. We find the answers from both methods
> correlate well.
Could you post measurements to this list that illustrate this point?
Erik Daniel, Ph.D. Mayo Foundation
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