Radio Part Tx Section - LG -P940 Service Manual

3.3 Radio Part Tx Section

The TX features 2 RF outputs, which are directly matched to 50
power amplifiers, which reduces significantly external component count. Those 2 outputs are high power, small
signal polar modulated outputs for the GSM and UMTS system, with low sensitivity to PA harmonics. They are
capable to perform GMSK or 8-PSK as well as UMTS modulation signals with excellent noise performance, thus
no inter-stage filter in between transceiver and PA is required. The transmitter outputs are broadband, one
covers all low bands (Band V, VI, and VII), the higher band output covers all GSM and UMTS bands Band I, II, III, IV,
IX and X. The output driver is capable to support high output powers to enable low cost single chain PA's.
The IC features additionally closed loop power control for GSM and for UMTS, thus supporting TRP requirements
in cooperation with the power amplifier and the antenna design. There is one input ball for the power detector
voltage coming from the PA, and one input ball for the RF signal fed back to the TRX. The complete loop circuits
are implemented in the digital domain, which enables a high reliability of the loop performance for both
standards.
DIG RF
3G
LGE Internal Use Only
1
C HIP
1 bit
sign
0
C HIP
1 bit
sign
[Figure 3-4] Single Chain PA's Tx Architecture
impedance for easy connection to external
AM-Path
TX-Disruptor
PM-Path
AM-Path
PM-Path
Feedback RX
to signal
chain
Detector ADC
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3. TECHNICAL BRIEF
Only for training and service purposes