Directional Coupler Check - Agilent Technologies 8719ET Service Manual

8719ET/20ET/22ET
8719ES/20ES/22ES
RF Network Analyzers

Directional Coupler Check

1. For the 8719ET/ES and 8720ET/ES, set the output power to −10 dBm by pressing
−10
Power x1
2. For the 8722ET/ES, set the output power to −15 dBm by pressing
For ES Models, set up the following
3. Connect an RF flexible cable from the output of the transfer switch (A74) directly to the
2.4 mm RF INPUT (J2) of the suspect sampler. Use 3.5 mm to 2.4 mm adapters where
necessary. This connection bypasses the step attenuator, bias tee, and the coupler.
IMPORTANT To disconnect the semirigid cable of the A74 transfer switch, it may be
necessary to disconnect additional semirigid cables and loosen the transfer
switch. Be careful not to damage the center pin when disconnecting the cable.
For ET Models, set up the following
4. For standard ET models, connect an RF flexible cable from the cable (W76) that
connects the M/A/D/S (A58) to the directional coupler (A62) to the 2.4 mm RF INPUT
(J2) of the suspect sampler. (Make the connection at the coupler end of the cable).
For ET Option 004 models, connect an RF flexible cable from the cable(W32) that
connects the M/A/D/S (A58) to the step attenuator (A69) to the 2.4 mm RF INPUT (J2)
of the suspect sampler. (Make the connection at the attenuator end of the cable.)
Checking the Operation of the Sampler
5. To measure the signal at the A sampler, on ET models press
(on ES models press
A
the transfer switch is being tested).
To measure the signal at the B channel, on ET models press
B (on ES models press
the transfer switch is being tested).
Compare the responses to the examples in
power levels in Table 8-2 on page
higher due to the reduced loss created by the bypassed components.
• If the trace is similar (with the exception of the coupler roll-off below 500 MHz) to
Figure 8-1 on page
or bias tee is lossy. Test the path by substituting the components one at a time and
comparing the response to
directly. Minor power variations are probably due to the flexible cable and are of no
concern.
• If the trace is abnormally low, the coupler is good and the sampler is at fault.
Troubleshoot the associated sampler by referring to
page 8-9.
Service Guide
.
or
TESTPORT 1
TESTPORT 1 or
8-5. Expect the nominal power level to be a little
8-6, the sampler is good. Therefore, the coupler, step attenuator,
Figure 8-1 on page
At Least One Signal Path Looks Normal
Meas
depending on which side of
TESTPORT 2
Meas
TESTPORT 2 depending on which side of
Figure 8-1 on page 8-6
8-6, or measure the insertion loss
"Sampler Voltage Check" on
Receiver Troubleshooting
−15
Power x1
INPUT PORTS
INPUT PORTS
and the nominal
8- 7
.