Agilent Technologies 4395A, Ручное изменение

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Reection Measurement (NA)
Reection Measurement (NA)
When making a reection measurement, the 4395A monitors the signal going to the DUT and
uses it as the reference . It compares the reected signal from the DUT to the reference signal.
The ratio of the incident and reected signals is the reection coecient of the DUT or , when
expressed in decibels , the return loss .
Reection measurements require the connection of a directional device , such as a directional
coupler , to separate the power reected from the DUT . This separation is necessary so that it
can be measured independently of the incident power (see Figure 10-7).
Figure 10-7. Reection Measurement
Multi-P ort T est Devices
When the device has more than one port, connect high-quality terminations (loads) to all unused DUT ports to
terminate them into their characteristic impedance (usually 50 or 75 ). If this is not done , reections o the unused
ports will cause measurement errors .
The S-parameter test set automatically switches the termination at the unused port for each S-parameter
measurement. When using a transmission/reection test set, terminate the unused input port of the analyzer with a
high quality load.
The signal reected from the DUT is measured as a ratio with the incident signal. It can
be expressed as a reection coecient, a return loss , or as SWR. These measurements are
mathematically dened as:
Examples of Applications 10-7