CCS Technical Documentation
NSB-9
Issue 1 04/03
Copyright
Nokia. All rights reserved..
Page 49
TX IQ Tuning
Calibrates GSM850 and GSM1900 TX I/Q signal DC-offset, amplitude and phase differ-
ence at middle channel. Tuning is done by sending '1'-bits to the modulator. Best modu-
lator balance is achieved when spikes at carrier frequency f0 and f0+67.71 kHz reach
minimum value.
Saved tuning values are:
TX I-channel DC-offset
TX Q-channel DC-offset
Amplitude difference between TX I- and Q-channels
Phase difference between TX I- and Q-channels
Tuning correctness is checked by measuring TX output spectrum at frequencies:
TX IQ f0
TX IQ f0 + 67.71 kHz
Table 4: TX IQ Tuning Limits
Band
GSM850
GSM1900
Item
Typical value
Low
limit
High
limit
Typical value
Low
limit
High
limit
TX I DC offset
-2...1
-6
6
-3...1
-6
6
TX Q DC offset
-2...1
-6
6
-1.5 ... 2
-6
6
Amplitude difference
-0.3 ... 0.2
-1
1
-0.5 ... 0.1
-1
1
Phase difference
88...92
84
96
90.5 ... 95.5
86
100
TX IQ f0
-55 ... -32
-90
-30
-49 ... -34
-90
-30
TX IQ f0 + 67.71 kHz
-68 ... -48
-90
-35
-63 ... -40
-90
-35