Chapter 3
GSM Asynchronous Mode Operation
Spectrum measurements
4460 GSM System Option and 4468 EDGE System Option
Version 12.20
153
Understanding the
measurement principle
The measurement is performed in the frequency domain. Level measurements are
performed at ±0 kHz, ±30 kHz, ±370 kHz, ±400 kHz, ±430 kHz, ±570 kHz,
±600 kHz, ±630 kHz, ±1170 kHz, ±1200 kHz, ±1230 kHz, ±1770 kHz, ±1800 kHz
and ±1830 kHz offset from the nominal carrier frequency through a 30 kHz
bandwidth filter. The measurement results are then displayed as vertical bars in
dBm. If the Peak Hold function is activated, the results settle after about
10 measurements.
The spectrum live display
The live display is updated continuously (as long as it has not been frozen).
The vertical axis of the spectrum live display is in dBm; the horizontal axis in
MHz.
The selection field
Max Level
allows to set the maximum power level to opti-
mize the vertical resolution.
The horizontal resolution of the display is fixed and follows the appropriate GSM
specification.
Entry field of the live display
Max Level —
This selection field allows to set the RF power level represented by
the top horizontal line of the live display.
Selections possible are: from +40 dBm to 0 dBm in steps of 10 dB.
NOTE
In addition to the requirements of the appropriate GSM specification, the RF
power level measured at 30 kHz
above and below
the specified offsets from
the carrier are displayed as well, in order to give additional indication when
the measurement result for a single frequency is close to the limits.
NOTE
For clarity of results, the 18 additional measurement results not required by
the appropriate GSM specification may be removed in the future.
NOTE
The value selected here should be equal or slightly higher than the expected
maximum RF power level on the carrier frequency in order to avoid overload
distortion and to achieve maximum vertical resolution.