Agilent Technologies 8753ET User Manual page 382

Operating Concepts
Measurement Calibration
Figure 7-28 Reflection Tracking E
These three errors are mathematically related to the actual data, S
data, S , by the following equation:
11M

S

11 A
S = E + ----------------------------------------- -
11M DF

1 –

If the value of these three "E" errors and the measured test device response were known
for each frequency, this equation could be solved for S
response. Because each of these errors changes with frequency, their values must be
known at each test frequency. These values are found by measuring the system at the
measurement plane using three independent standards whose S
frequencies.
The first standard applied is a "perfect load," which makes S
measures directivity. See
the measurement plane. All incident energy is absorbed. With S
solved for E , the directivity term. In practice, of course, the "perfect load" is difficult to
DF
achieve, although very good broadband loads are available in the compatible calibration
kits.
7-44
RF

E

RF

E S

SF 11 A
Figure 7-29. "Perfect load" implies a reflectionless termination at
, and measured
11A
to obtain the actual test device
11A
is known at all
11A
= 0 and essentially
11A
= 0 the equation can be
11A