Nokia NSB-7 Series Service Manual page 214

NSB-7
Service Software Instructions
4. AM suppression tuning
AM suppression calibration is for tuning four Hagar parameters to get as small RSSI
value as possible.
For AM-suppression calibration external signal generator with AM-modulation is
needed.
Signal generator setup: AM-modulation, fmod = 1 kHz, mod. depth = 83% f =
ch(default)+10 MHz, P = -26 dBm (GSM 1900)
Test limits for AM-calibr. results: -86 dBm (GSM 1900)
NOTE! Base level must be adjusted manually because the calculation most often fails.
5. I/Q Modulator Alignments
See chapter "Service Software Instructions" and section "TX I/Q... command" for further
information.
Procedure:
Connect the spectrum analyser to the service box JBU-6. The recommended spectrum
analyser settings are: span 200 kHz, resolution BW 10 kHz, video BW 1 kHz, sweep 1 s,
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 GSM 1900 is 661 (1880
MHz).
• Select the "TX I DC offset" option and adjust the level of the centre frequency
Page 108
CHF
–67.71 kHz
D.C. offset
tunings:
Set this value
to minimum
> 30 dB
ãNokia Mobile Phones Ltd.
PAMS Technical Documentation
+67.71 kHz
Amplitude &
> 35 dB
phase difference:
Set this value
to minimum
Issue 1 06/00