Agilent Technologies 8753ET User Manual page 386

Operating Concepts
Measurement Calibration
Two-Port Error Model (ES Models Only)
The error model for measurement of the transmission coefficients (magnitude and phase)
of a two-port device is derived in a similar manner. The potential sources of error are
frequency response (tracking), source match, load match, and isolation as shown in Figure
7-34. These errors are effectively removed using the full two-port error model.
Figure 7-34 Major Sources of Error
The transmission coefficient is measured by taking the ratio of the incident signal (I) and
the transmitted signal (T). Refer to Figure 7-35. Ideally, (I) consists only of power delivered
by the source, and (T) consists only of power emerging at the test device output.
Figure 7-35 Transmission Coefficient
As in the reflection model, source match can cause the incident signal to vary as a function
of test device S . Also, since the test setup transmission return port is never exactly the
11A
characteristic impedance, some of the transmitted signal is reflected from the test set
port 2, and from other mismatches between the test device output and the receiver input,
7-48