Tx Iq Tuning - Nokia NSB-9 Service Manual

CCS Technical Documentation

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
Band
Item
TX I DC offset
TX Q DC offset
Amplitude difference
Phase difference
TX IQ f0
TX IQ f0 + 67.71 kHz
Issue 1 04/03
Table 4: TX IQ Tuning Limits
GSM850
Low
Typical value
limit
-2...1 -6
-2...1 -6
-0.3 ... 0.2 -1
88...92 84
-55 ... -32 -90
-68 ... -48 -90
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GSM1900
High
Typical value
limit
6 -3...1
6 -1.5 ... 2
1 -0.5 ... 0.1
96 90.5 ... 95.5
-30 -49 ... -34
-35 -63 ... -40
NSB-9
Low High
limit limit
-6 6
-6 6
-1 1
86 100
-90 -30
-90 -35
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