HP 54753A User Manual page 130

11
Figure 7-13
Narrow Trace
Voltage
1
2
3
4
Single-ended TDR Measurements
Measuring Transmission Line Impedance
At the bottom of the display, read the number of volts for the narrow
trace discontinuity (Figure 7-13).
In this case, the voltage, vd1, is approximately equal to 238.834 mV.
Substituting and solving for p we have:
238.834 200
p = --------------------------------- -
therefore,
×
Z = 50Ω
Instead of calculating the impedance from the measured voltage, we can have
the oscilloscope calculate the impedance. Before we can do this we must first
establish normalization and the reference plane at the end of the cable
connected to the demo board. This requires a very accurate low reflection 26.5
GHz 50 ohm load, such as the HP 909D.
Press the
TDR/TDT Setup
Press Normalize response . . .
Disconnect the cable from the demo board.
Press the
Establish normalization & ref plane
7-22
–
= 0.19417
200
1 + 0.19417
---------------------------- = 74.09565Ω
1 0.19417 –
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