Time domain response of the test set can be used to identify problems in the RF path. The plots below
show typical time domain responses of the HP
and 8515A test sets. These can
be used as rough standards when trying to locate a problem in the RF path. Keep in mind that the
absolute location in time and absolute height of the responses will vary from test set to test set. The
significant factor is the relative height of the main impulse (determined by the calibrated short) and the
discontinuities. Discontinuities that may be causing a problem will usually stand out as being much
greater than the typical response.
Set up the system as follows to obtain a time domain trace:
1. Connect a short or shielded open to the test set port
2.
Press
[PRESET] [DOMAIN] [TIME BAND PASS]
STIMULUS
[MENU] [NUMBER OF POINTS]
[0]
[LOG
3.
Set the
START/STOP TIME, SCALE,
and
REF VALUE
as indicated in Table 5-3, below.
Table 5-3. Suggested Parameter Values for Time
Domain Troubleshooting
Test Set Start Time Stop Time Scale
REF Value
Refer to
Figure
HP
-1.0 ns 11.0 ns 10
- 2 0
5-4
HP
- 6 . 0
6.0
ns
5
- 2 0
5-5
4. For the HP 8514A or
you can check the port 2 responses using the same set-up as described
above except connect the termination to port 2 and select S22 instead of
Peaks in the trace
that are significantly greater than those shown indicate a possible loose or bad connection in the
RF path at that location.
Figure 5-4. HP 8512A Typical Port Response
5-6 Test
Troubleshooting
HP
Test Sets