Trouble Shooting Guide, Advanced
4/00021-3/FEA 209 544/25 C
Ericsson Mobile Communications AB
39(78)
Fig. 12.2
The proportion for the amplitude is correct at Power level 5 (for EGSM900) and Power level
0 (for GSM1800).
The Offset level is the highest possible voltage before the power amplifier starts to transmit.
The Offset voltage compensates for the differences of voltage fault between different power
amplifiers and is produced in N700.
Table 12.1 below shows the limits for maximum power levels at transient disturbances.
EGSM 900
GSM 1800
Parameter
Max
Max
Units
Fc+400kHz
-19
-22
dBm
Fc-400kHz
-19
-22
dBm
Table 12.1
”Measure Transient Spectra” is a part of the radio calibration in EFRA.
It is performed after the power calibration and measures the power levels at the middle
channel frequency (± 400 kHz) of the transmitter.
12.2 How to measure the transient spectrum
EGSM900:
Power up the board and start it in the test program.
Start the transmitter in switched mode at channel 64 and power level 5.
Before performing a transient spectrum measurement you have to make sure the spectrum
analyser has got the correct amplitude compensation.
To do this you use a phone with a known output power and start the transmitter in switched
mode at power level 5.
Then you compensate the spectrum analyser until the correct output power is achieved.
Convenient settings for this are:
CF – 902.8, SPAN – 0 MHz, RBW – 300 kHz, VBW – 100 kHz and SWEEP – 0.8 ms.)