HP 85027A/B/C Performance Tests
the bridge does not meet specifications, perform the troubleshooting procedures
outlined in Section 8.
Above 2 GHz:
7.
On the sweep oscillator, set the start and stop frequencies to match line 2 of Table
4-1, Directivity Performance Test Record.
8.
Perform a short/open calibration.
9.
Connect the sliding load to the test port of the bridge. (Refer to the sliding load’s
Operating and Service Manual if need be.)
10.
On the HP 8757A press [AUTOSCALEI to position the trace on the display.
Slowly move the sliding load back and forth: the trace should change slightly as
the phase of the sliding load reflection changes. For several frequencies on the
display, note the maximum and minimum measured return loss for various sliding
load positions.
11.
For each frequency, the maximum and minimum measured return loss values
correspond to the directivity signal and the sliding load signal adding and
subtracting. You can separate these two signals with the Signal Separation Chart,
Figure 4-3. Calculate the difference in dB between the maximum and minimum
measured return loss for each frequency and locate this value on the veitical axis
of Figure 4-3. Draw a horizontal line across the chart from the point just located
and note the two places where it intersects the curves. The intersections are the
two correction values in dB. Add each of them to the minimum measured return
loss. The i-esulting two corrected values are the directivity signal and the sliding
load reflected signal.
4-4
