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Below 2 GHz:
3.
On the HP 8350B set the START and STOP frequencies to the frequencies on the
first line of Table 4-1, Directivity Performance Test Record.
4.
Perform a short/open calibration by pressing [CAL] on the HP 8757A and then
following the prompts on the CRT.
5.
Attach the fixed load to the test port of the HP 85027. On the analyzer, press
[CURSOR] and softkeys [CURSOR ON] and [MAX] to find the point of minimum
return loss (the high point on the trace). Record the displayed CURSOR value on
the appropriate line of Table 4-1. Note that this value represents the scalar sum of
directivity signals (the desired measurement plus signals reflected from the fixed
load (undesired error). Thus fixed load quality directly affects the quality of
directivity measurements.
MEASURED
VALUE
Direct
(p)
lvi ty
(dB)
30
.030
6
.
31.1
.028
.026
31.7
32.4
.024
.022
33.2
34.0
.020
.018
34.9
.016
35.9
.014
37
1
.
38.4
.012
40
.010
. 0
41.9
.008
-
44. 4
.006
-
.004-
48.0
54.0
.002
0-
aD
0
aD
Figure 4-2. Probable Range of Measurable Directivity Values
6.
Refer to Figure 4-2. The shaded ai-eas in this figure represent the probable range
of measureable values for each of the three specified directivity values: 34 dB, 36
dB and 40 dB. On the horizontal axis, locate the fixed load's reflection coefficient
or its specified retum-n loss (convert from SWR if necessary). Move up from this
point to the upper limit of the shaded area between the appropriate diagonal lines.
Allowing for load erroi-, any directivity measurement that falls below this upper
limit indicates with 90% probability that the HP 85027
HP 85027A/B/C Performance Tests
.001 .002
.003 .004 .005
60
54
50.5
48
SPECIFIED p OR RETURN LOSS OF LOAD
.006
.007 .008 .009 .010
46
44.4
43.1
42
w4bin specifications If
i~-
tic.
4-3
(p)
40
40.9
Return Loss
(dB)
(
~
~
-,
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