Agilent Technologies 8753ET User Manual page 409

mismatches and losses. In a reflection measurement, the source match error signal is caused by some of
the reflected signal from the test device being reflected from the source back toward the test device and
re-reflected from the test device. This is illustrated in
source match error signal is caused by reflection from the test device that is re-reflected from the source.
Source match is most often given in terms of return loss in dB: thus the larger the number, the smaller the
error.
Figure 7-22 Source Match
The error contributed by source match is dependent on the relationship between the actual input impedance
of the test device and the equivalent match of the source. It is a factor in both transmission and reflection
measurements. Source match is a particular problem in measurements where there is a large impedance
mismatch at the measurement plane. (For example, reflection devices such as filters with stop bands.)
Load Match
Load match error results from an imperfect match at the output of the test device. It is caused by impedance
mismatches between the test device output port and port 2 of the measurement system. Some of the
transmitted signal is reflected from port 2 back to the test device as illustrated in
this wave may be re-reflected to port 2, or part may be transmitted through the device in the reverse
direction to appear at port 1. If the test device has low insertion loss (for example a filter pass band), the
signal reflected from port 2 and re-reflected from the source causes a significant error because the test
device does not attenuate the signal significantly on each reflection. Load match is usually given in terms of
return loss in dB: thus the larger the number, the smaller the error.
Figure 7-23 Load Match
The error contributed by load match is dependent on the relationship between the actual output impedance
of the test device and the effective match of the return port (port 2). It is a factor in all transmission
measurements and in reflection measurements of two-port devices. The interaction between load match
and source match is less significant when the test device insertion loss is greater than about 6 dB. However,
source match and load match still interact with the input and output matches of the DUT, which contributes
Figure 7-22. In a transmission measurement, the
Operating Concepts
Measurement Calibration
Figure 7-23. A portion of
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