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HP 85027A/B/C Performance Tests
2
4
6
8
10
12
14
16
18
20
22
24
26
CORRECTION IN dB
Figure 4-3. Signal Separation Chart
12.
Usually the larger return loss value is the measured directivity error. You can
verify this by performing the following step.
13.
Slowly retract the center conductor of the sliding load about 2mm. This will
introduce a discontinuity at the HP 85027 test port and change the measured
directivity. Repeat steps 10 and 11 above. After the signals are separated, one of
the two should match one of the two separated signals from the first
measurement. The matching value is the return loss of the sliding load. The other
separated value from the first measurement is the directivity of the HP 85027.
14.
Enter the directivity on the Directivity Performance Test Record, Table 4-1.
15.
Although the signal separation procedure removes reflections of the load itself, the
mismatch of the sliding load connector and airline introduces reflections and
uncertainties. To estimate these uncertainties, refer to Figure 4-2. Locate the
specified return loss of the sliding load airline and connector on the horizontal axis
(convert from SWR). Move up from this point to the upper limit of the bridge
specified directivity corresponding to the sliding load's return loss for this
frequency range. Enter this value in Table 4-1.
16.
Set the start and stop frequencies of the source to the next band of interest in
Table 4-1. Repeat steps 8 through 15.
4-5
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