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Overview
In the FieldFox, both 1-port and 2-port measurement types use a different
configuration setup from the HP/Agilent 8508A Vector Voltmeter.
Typical 8508A measurement configuration –as shown in the 8508A manual.
The above block diagram requires an external source and directional coupler to
measure the electrical length of a DUT or cable to be trimmed. Separate paths
are used to measure the Incident signal (A) and Reflected signal (B). To measure
the ratio of the Reflected/Incident signals, you were required to select B/A for
both the Magnitude and Phase display.
In the following FieldFox block diagram, the source and directional coupler are
inside the instrument. This allows you to connect the DUT to ONLY the FieldFox
PORT 1 with NO external instruments, in order to make 1-Port Cable Trimming
measurements.
VVM (Vector Voltmeter) Mode
FieldFox block diagram
The
R
receiver measures incident signal
(green line) out of the source.
The
A
receiver measures reflected signal
(red line) from the end of the DUT (black
line).
In VVM mode, the 1-Port Cable Trimming
display ALWAYS shows ratioed (A/R)
measurements which is the electrical
length of the DUT.
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