![Rohde & Schwarz FSH4 Operating Manual Download Page 215](http://html.mh-extra.com/html/rohde-and-schwarz/fsh4/fsh4_operating-manual_1477834215.webp)
R&S FSH
Digital Modulation Analyzer
Measurements on 1xEV-DO Signals
Operating Manual 1309.6275.12 - 14
196
7.3.5.5 Changing the PN Offset
The standard uses the PN Offset to distinguish between base stations. The PN offset
determines the offset in the circulating PN sequence in multiples of 64 chips with
reference to the event second clock trigger.
Each signal is spread with a Walsh code of a length of 64 or 128 and a pseudo-random
noise code (PN code) of a length of 215. Each BTS sector in the network is assigned a
PN offset in steps of 64 chips.
If you use an external or GPS sync trigger, you have to adjust the PN Offset according
to the base station / sector you are measuring.
M
Press the MEAS key.
M
Press the "Signal Settings" softkey.
M
Select the PN OFFSET menu.
M
Enter the PN Offset you need (between 0 and 511).
7.3.5.6 Synchronizing to a Base Station Using a GPS Receiver
If you use a GPS receiver while performing measurements on a base station, you can
synchronize the sweep via the GPS receiver.
M
Press the SWEEP key.
M
Press the "Trigger" softkey.
M
Select "GPS Sync" menu item.
The R&S FSH now synchronizes the sweep to the signal using the GPS receiver.
7.4 Measurements on 1xEV-DO Signals
Equipped with the software application R&S FSH-K47, you can perform measurements
on downlink 1xEV-DO signals in accordance to the 3GPP2 standard with your
R&S FSH.
M
Press the MODE key
M
Press the "Dig Mod Analyzer" softkey.
M
Select the "1xEVDO BTS" menu item.
The R&S FSH starts the signal analysis.
After you have started the measurement, the R&S FSH first records a section of the
signal that lasts approximately 27 ms (or about 1 Sync Frame Period). If the instrument
is in a triggered mode (external or GPS trigger), it then searches for the start of the PN
code in the vicinity of the PN offset you have entered. If you are using the automatic
PN Offset, the R&S FSH performs a full search for the PN offset and reports the PN
found. For a "free run" situation, the R&S FSH searches for the start of the PN
sequence over the entire signal length.