Specifications

(TDR) you may feel more comfortable with step response, as the
displays are similar.
The lowpass-step response for a resistive impedance is a positive level
shift for R>Z
0
and a negative level shift for R<Z
0
. The height of the
response is equal to the reflection coefficient
r=
-
+
RZ
RZ
0
0
The step response for a shunt capacitance is a negative peak, and for a
series inductance it is a positive peak (Figure 8-3).
An example of using the lowpass-step response is cable-fault location.
In the frequency domain, a cable with a fault exhibits a much worse
match than a good cable. Using lowpass-step response, both the
location of the discontinuity and the information about its type are
available (Figure 8-4).
In the above example, the dip in the display shows the
shunt-capacitive response caused by a crimp in the cable. The
response at the end of the cable shows the step-up that is typical of an
open (Figure 8-3).
The MS462XX bandpass mode gives the response of the DUT to an
RF-burst stimulus. Two types of response are available: impulse and
phasor-impulse. An advantage of the bandpass mode is that any
frequency range can be used. Use this mode with devices that do not
have a dc or low-frequency path.
TIME TIME DOMAIN
DOMAIN MEASUREMENTS
MS462XX OM 8-5
LOWPASS STEP RESPONSE
l
TDR Measurement
l
Location of Discontinuities
l
Information on Type of Discontinu
-
ities
CIRCUIT ELEMENTS
R>Z
O
SHUNT C
SERIES L
IMPEDANCE
O
R<Z
11
S REAL
Lowpass Step Response
Figure 8-3. Lowpass-Step Response
40.000cm
0.000mm
1
3
CABLE
2
OPEN
Figure 8-4. Example of Lowpass-Step Response
BANDPASS MODE
l
Calculates Impulse or
Phasor-Impulse Response
l
Uses Any Frequency Range
l
Used When Device Does Not Have
a DC or Low-Frequency Path