HP 54753A User Manual page 227

Improving Time Domain Network Measurements
Removing Measurement Errors
Putting It All Together
The actual normalization of a DUT response is accomplished in two steps. A
stored waveform, derived in the normalization and which represents the
systematic errors, is subtracted from the measured DUT waveform. This result
is then convolved with the digital filter to yield the response of the DUT,
normalized to an ideal step input with the user-specified risetime.
Figure 10-16 illustrates the power of normalization. It shows discontinuities in
a transmission path measured using TDR. The bottom waveform was measured
in a test system with an approximate risetime of 35 ps. The top waveform is
the bottom waveform normalized to 20 ps risetime. Note that in the bottom
waveform there appears to be only one inductive discontinuity. Using
normalization, it becomes obvious that there are actually two inductive
discontinuities. Because it is difficult to build a 20 ps risetime step stimulus
with a clean response and a test system with adequate bandwidth to measure
it, this measurement probably could not have been made without normalization.
Figure 10-16
The top waveform is the same signal as the bottom waveform, except that it has been normalized.
Normalization reveals that there are actually two inductive discontinuities, rather than one as
shown in the bottom waveform
10-21