Digital Signal Processing Reference
In-Depth Information
L
v
s
R
s
=
50
Ω
A
Z
0
=
50
Ω
Z
0
=
50
Ω
R
t
=
50
Ω
0-2
V
2
1.8
1.6
1.4
1.2
Area
=
A
ind
1
0.8
0.6
0.44
0.46
0.48
0.5
0.52
0.54
0.56
0.58
0.6
Time, ns
Figure 3-45
The area under the reflection can be used to estimate the inductance.
v
s
R
s
=
50
Ω
A
Z
0
=
50
Ω
Z
0
=
50
Ω
R
t
=
50
Ω
C
0-2
V
1.2
1
0.8
0.6
Area
A
cap
=
0.4
0.2
0
0.3
0.4
0.5
0.6
0.7
0.8
Time, ns
Figure 3-46
The area under the reflection can be used to estimate the capacitance.
For long rise times or very small inductance values, the area under the curve will
be masked by a rise time similar to the reflections in Figure 3-37.
Capacitive Structures
In a TDR measurement, narrow dips such as that depicted
in Figure 3-46 are indicative of an capacitive component such as a probe pad or
a via pad. Assuming that the input step has a sufficiently fast rise time, the value
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