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S
22
) are not desired, then a circulator is not required. Instead, a through
line should be connected between connectors C1 and C2 (Figure 1-5). The
MS4782A is shipped from the factory with this through line in place.
1-10 K FACTOR K factor is a parameter which is sometimes used to indicate the stability
of an amplifier. K factor is a function of all four S parameters and is de
-
fined by the formula
K
SS
SS
=
--+1
2
11
2
22
22
11 21
D
Where
D =S
11
S
22
-S
12
S
21
The necessary and sufficient condition for unconditional stability is that
K>1 and
D<1
.
K factor is available as the sixth choice in the S parameters menu (first
five choices are: S
11
,S
22
,S
21
,S
12
and ALL). The same conditions and
setup as S-parameter measurements including a full 12-term calibration
applies to this measurement. The result is “dynamic” meaning that the
above formula is applied at each point for each sweep as the S parame-
ters are reported to the PC over the GPIB.
1-11 ADAPTIVE P STOP Adaptive P stop lets users enter a gain compression value at which the
program will adjust the final P
in
value during a power sweep. For exam-
ple, if user sets 3 dB P-stop, the program commands the execution of one
sweep, find P
in
value where 3 dB gain compression occurs, back up 1 in
-
crement, and reset this as the upper bound of the power sweep.
1-12 SOFTWARE
DESCRIPTION
The ME7840A software exhibits an open architecture that has been de
-
veloped using standard C++ and Visual Basic languages. The software is
compiled as an Active X exe module.
The software resides in the System Controller (PC), and communicates
with the Direct Receiver Access (DRA) Scorpionâ Vector Network Mea
-
surement System (VNMS) via the GPIB bus. Optionally, the ME7840A
software can also interface with additional GPIB capable test equipment,
such as a multimeter or a power meter.
1-13 TEST EXECUTIVE The Test Executive is an optional layer of test management software. The
ANRITSU measurement and display software does not require a separate
Test Executive, even though it can operate in conjunction with one such
as the National Instruments TestStand or customer’s proprietary Test
Executive. In the absence of a separate test executive, the ANRITSU soft
-
ware can be operated on a stand-alone basis or can be called directly by a
Microsoft Windows 95/98/2000 or NT program such as Word, Excel or Ac
-
cess that supports Visual Basic function calls.
GENERAL INFORMATION K FACTOR
ME7840A OMM 1-9