User Guide

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