Nokia NSB-9 Service Manual page 123

CCS Technical Documentation
*) Tuning may return values between -6...37 but values between 0...31 are saved to phone
permanent memory. Values -6...0 are round up to 0 and values 31...37 are round down to
31.
RX Calibration
Description
Calibrates 26 MHz voltage controlled reference oscillator VCTCXO at the beginning of
GSM850 receiver gain (RSSI) tuning. AFC control voltage for VCTCXO is produced using
11-bits DA-converter inside UEM RF IC. AFC DAC value (AFC VALUE) which gives correct
VCTCXO output frequency is defined by measuring RX I/Q signal frequency and by adjust-
ing AFC to set correct frequency. AFC VALUE is used as an init value when phone has not
found a base station signal yet.
After correct AFC VALUE is found, AFC value is changed to different value. RX I/Q fre-
quency is measured again and AFC SLOPE (frequency change divided by AFC value
change) is calculated.
GSM850 and GSM1900 RX chains gain are tuned at middle channel.
Band
Item
AFC VALUE
AFC SLOPE
RSSI 0
RSSI 1
RSSI 2
RSSI 3
RSSI 4
RSSI 5
RSSI 6
RSSI 7
RSSI 8
RX AM Suppression Calibration
Description
Calibrates GSM850 and GSM1900 RX mixer local signal DC-levels to achieve best rejec-
tion for AM modulated interferences. Calibration needs external AM modulated signal
applied to the phone. If tuning is successful, either LOP or LOM result in both branch (I
Issue 1 04/03
Table 2: RX Calibration Limits
GSM850
Low
Typical value
limit
-300...0 -350
240...260 150
74...76 65
84...86 75
94...96 85
101...103 91
111...113 101
121...123 111
131...133 121
141...143 131
151...153 141
Copyright Nokia. All rights reserved..
GSM1900
High
Typical value
limit
350 NA
350 NA
85 67...71
95 77...81
105 87...91
111 96...99
121 106...129
131 116...119
141 126...129
151 136...139
161 146...149
NSB-9
Low High
limit limit
NA NA
NA NA
59 79
69 89
79 99
88 108
98 118
108 128
118 138
128 148
138 158
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