Specifications

20
Appendix D—Optimizing power sweep range
Power sweep range will be reduced if a power flat-
ness correction is used in combination with power
sweep. If flat test port power is required, there is
no way to avoid this.
If the source has step attenuators installed, and a
power flatness correction is used with power
sweep, the available sweep range will be further
reduced. This reduction is due to the source setting
the attenuator for the optimum ALC (automatic
leveling control) range. This loss in sweep range
can be compensated for using one of the following
two methods. Both methods require a computer to
implement a work around which allows better use
of the ALC range in the 8360 synthesizer when
using power sweep plus flatness correction.
The first method involves using a computer con-
nected directly to the source to make the modifica-
tions.
1. Read the flatness correction array from the
8360. Determine the average.
2. Determine the average amplitude correction the
array is providing (max+min)/2 (eg. (–10 dBm +
–30 dBm)/2).
3. Subtract this number from each of the numbers
in the array and put this modified array back into
the 8360.
4. Use that same “average correction” and input
that as a “power offset”.
The net result will be the same power out of the
8360, but the attenuators will be “faked out” and
allow as much of the ALC range to be used as pos-
sible. (Remember that some sweep range will still
be lost because of the flatness correction.)
The second method involves connecting the com-
puter to the 8510 and using the “pass-through”
address to access the source. Pass-through allows
you to WRITE to the source, but not READ them
from the source, so an alternate method must be
used.
Since you can’t read the actual array from the
8510, you have to find another way to get the same
data. With the 8510, you can read the power to the
test port by looking at “a1” instead of S
11
, S
21
, etc.
The procedure is as follows.
1. Read the “a1” data with flatness off into a com-
puter.
2. Read the “a1” data with flatness on.
3. Calculate the difference in dB between the two
traces and determine the max and min correction.
From that, calculate the “average correction.”
4. Build a new flatness array, subtracting the “aver-
age correction” as in the previous process.
5. Write this to the 8360 using pass-through.
6. Set the power offset also using pass-through.
Note: You must make sure you are operating in the
linear region of the test set, otherwise the offset
will not be correct.