
PAMS
Technical Documentation
NSM–1
Tuning Instructions
Page 14 Original 10/98
3. I/Q Modulator Alignments
I/Q modulator alignments are performed in PCN band. If GSM band has
been selected and I/Q alignment is started, the service software asks to
change to PCN band. If the user wants to continue in GSM, the adjusted
values can only be saved to PC memory, not to phone’s EEPROM. After
changing to PCN band values from PC memory are available, and if the
modulator adjustment is good, also the values can be saved to phone’s
EEPROM. See chapter ”Service Software Instructions” and section ”TX
I/Q... command” for further information.
Procedure:
Connect the spectrum analyzer to the phone antenna connector. The rec-
ommended spectrum analyzer settings are: span 200 kHz, resolution BW
10 kHz, video BW 1 kHz, sweep 500 ms, input attenuation 30 dB.
– From
RF controls
menu make sure that TX data type is 1.
– Go to
TX I/Q tuning
menu. The alignment channel for PCN is 700
(1747.8 MHz).
– Select the ”TX I DC offset” option and adjust the level of the centre fre-
quency (CHF) to minimum.
– Select the ”TX Q DC offset” option and adjust the level of the CHF
again to minimum.
– After finding both minima change ”TX I DC offset” by step or two from
the current value to both directions to see, whether better minimum
can be found for CHF.
– Select the ”Amplitude Difference” option and adjust the level of the un-
wanted sideband CHF + 67.71 kHz to minimum.
– Select the ”Phase Difference” option and dajust the level of CHF +
67.71 kHz again to minimum.
– After all the minima have been found press ”Save” button to store the
values to phone EEPROM.
Targets:
The level of the centre frequency CHF should be at least 30 dB down to
the wanted sideband CHF - 67.71 kHz.
The level of the unwanted sideband CHF + 67.71 kHz should be at least
35 dB down to the wanted sideband CHF - 67.71 kHz.
Alignment verification in GSM band:
– Go to
Product ––> Initialize ––> Normal mode
. This is needed to give
a SW reset for the phone. Which in turn is needed to get the aligned
I/Q values in use.
– Go to
Product ––> Band ––> GSM
– Go to
RF controls
menu and start transmission on channel 60, power
level 10, TX data type 1.