for some weeks now, I'm glad
to have an Agilent 54754A based TDR in my lab
to analyze PCB structures. On one PCB I analyzed
the transition from the PCB wave guide into
an RF connector and found a positive bump indicating
a more or less inductive behaviour for this
The system allows the positioning
of two markers and calculates the excessive
reactance in between these markers. This is
really valuable to determine the correct compensation,
or to find a way to reduce the excess.
the section of interest I get round about 630nH
of inductance if I place the markers left and
right of it. So far so good.
to me is the behaviour that I see if I move
the markers closer together to cover only a
part of this inductive discontinuity. At a certain
point, when the left quarter of the discontinuity
is outside the markers the display jumps over
and starts showing fF and further in pF values.
I'd like to make clear, that all the curve in
between the markers is clearly >50Ohm.
I have started a support case and received a
number of AppNotes on TDR measurements, but
no clear statement yet. The system is in the
market for quite some time and I checked I use
the latest software from Aug2011.
I will try to make screenshots visible here
in this thread to illustrate the description
and I'm still searching the solution in between
screen an chair fo course.
I wonder if somebody has a similar system
available, or has a good explanation for this
Many Thanks, Thomas.