Chapter 3
GSM Asynchronous Mode Operation
Spectrum measurements
152
4460 GSM System Option and 4468 EDGE System Option
Version 12.20
ACPM transient spectrum
measurements
The mobile under test sends bursts with fast rising and falling edges. These
switching transients cause interference in the adjacent channels. In order to
minimize that interference, the mobile has to be compliant with the appropriate
GSM specifications.
To call the menu, simply push the
[ACPM trans.]
marker tab.
On first sight
The mobile’s transient spectrum is displayed graphically in the menu’s live
display for the discrete frequencies specified by the appropriate GSM specifica-
tion. The live display is updated continuously. To read the exact measurement at
any position, simply use the display markers.
The current main parameters and the status are displayed in the lower right
corner of the menu.
The softkeys provide access to important tools of the spectrum analyzer.
A glance into the GSM
specifications
The ACPM measurements refer to section 4.2 (Output RF Spectrum) of specifica-
tion GSM 11.10 (Mobile conformance specification; Radio transmission and
reception).
Section 4.2.2 specifies measurements for the ‘spectrum due to switching tran-
sients’.
These measurements are taken through a 30 kHz filter (resolution bandwidth;
100 kHz video bandwidth) at offsets of ±400 kHz, ±600 kHz, ±1200 kHz and
±1800 kHz from the carrier.
Measurements are ungated (i.e. measurements include the edges and the
midamble).
The GSM specification then specifies that a single measurement shall be the
search for the peaks of at least 10 bursts (peak-hold mode).