Near-eld data collection
Frequency multiplexing during a data scan/acquisition can result in a misalignment of
the rectangular near-eld grid between forward and reverse data scan directions. This
introduces an error into the measured near-eld data set which results in a far-eld pat-
tern. One way to eliminate this error is to always collect data measurements in the same
scan direction, but this would double the data scan acquisition time. Another approach
is to scan frequencies in reverse order on reverse scans. Using this reverse sweep in
conjunction with correct triggering between forward and reverse passes insures that
each frequency set is spatially aligned on the rectangular near-eld grid. This technique
requires an RF source that supports reverse frequency list mode of operation. The PNA
network analyzer includes reverse sweep and edge triggering capability specically
designed for antenna measurements.
Figure 27. Reverse sweep with synchronous triggers.
Functional test
A software utility is available for the PNA network analyzer that helps verify that a PNA
has been correctly congured with an external source for making antenna measure-
ments. The utility congures the PNA as a receiver and communicates with external
sources over GPIB. The triggering is done by handshaking the PNA and external sources
using the TTL trigger in and trigger out capabilities on the PNA and PSG. The software
does not verify specications, but is useful in determining that a valid connection has
been established between the analyzer and the source.
Go to http://na.tm.keysight.com/pna/antenna to download the program.
F1 F2 F3 F1 F2 F3 F1 F2 F3
F1 F2 F3
F3 F2 F1 F3 F2 F1 F3 F2 F1 F3 F2 F1
F1 F2 F3 F1 F2 F3 F1 F2 F3 F1 F2 F3
F1 F2 F3
F1 F2 F3 F1 F2 F3 F1 F2 F3
Forward
Forward
Reverse
Reverse
Bi-directional scanning can introduce errors in measured positions
Solution: Reverse frequency sweep and synchronous triggers
43 | Keysight | Antenna Test – Selection Guide
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