Improving Time Domain Network Measurements
Removing Measurement Errors
10-11
Figure 10-8
Normalization improves the ability to distinguish two discontinuities by decreasing the system
risetime.
a. System risetime = 45 ps.
b. System risetime = 100 ps.
c. System risetime = 50 ps.
d. System risetime = 20 ps.
e. System risetime = 10 ps
Normalizing the Test System
The normalization process characterizes the test system and is made with all
cables and connections in place but without the DUT.
Removing Systematic Errors
The first part of TDNA normalization removes systematic errors due to trigger
coupling, channel crosstalk, and reflections from cables and connectors.
For TDR, this is done by replacing the DUT with a termination having an
impedance equal to the characteristic impedance of the transmission line. If
the termination is properly matched, all of the energy that reaches it will be
absorbed. The only reflections measured result from discontinuities along the
transmission line.
For TDT, this normalization step is done with nothing connected to the
oscilloscope input.
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