Chapter 3
GSM Asynchronous Mode Operation
Spectrum measurements
4460 GSM System Option and 4468 EDGE System Option
Version 12.20
149
On first sight
The mobile’s modulation spectrum is displayed graphically for the discrete
frequencies specified by the appropriate GSM specification in the menu’s live
display. The live display is updated continuously. To read the exact measurement
at any position, simply use the display markers.
The measurement results shown are relative to the level at the center frequency.
The level display at the lower left of the menu displays the absolute level at the
center. This allows you to calculate the absolute values at each of the displayed
frequencies.
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 4.2.1 specifies various measurements for the ‘spectrum due to modula-
tion and wide band noise’.
The most important measurements are through a 30 kHz filter (resolution band-
width; 100 kHz video bandwidth) at offsets of ±100 kHz, ±250 kHz and all multi-
ples of ±200 kHz from the carrier up to (and including) ±1800 kHz.
The signal is measured over the useful part of the burst (i.e.
not
including the
rising and falling edges of the burst), also excluding the midamble (i.e. the
training sequence).
The GSM specification then specifies that the single measurement results shall
be averaged over 200 bursts and displayed in relation to the RF power level
measured (with a 30 kHz bandwidth) at the carrier frequency.
NOTE
The ‘carrier frequency’ is the frequency of the TCH used for this measurement.