LGE Internal Use Only
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
3. TECHNICAL BRIEF
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3.2 GSM Mode
3.2.1 GSM Receiver
The Dual-mode L704i’s receiver functions are split between the three RFICs as follows:
• UMTS-800 operation uses the RFR6275 Receiver ICs to implement the receive signal path,
accepting an RF input and delivering analog baseband outputs (I and Q).
• GSM-900, DCS-1800, and PCS-1900 modes both use the RTR6275 IC only. Each mode has
independent front-end circuits and down-converters, but they share common baseband circuits (with
only one mode active at a time). All receiver control functions are beginning with SBI
2
-controlled
parameters.
RF Front end consists of antenna, front end module (LMSP54MA-543) which includes three RX saw
filters(GSM900, DCS and PCS). The front end module allows multiple operating bands and modes to
share the same antenna. In L704i, a common antenna connects to one of seven paths: 1) UMTS-800
Rx/Tx, 2) UMTS-2100 Rx/Tx, 3) GSM-900 Rx, 4) DCS-1800 Rx, 5) PCS-1900 Rx , 6) GSM-900 Tx, 7)
DCS-1800 PCS-1900 Tx.
UMTS operation requires simultaneous reception and transmission, so the UMTS Rx/Tx connection is
routed to a duplexer that separates receive and transmit signals. GSM900, DCS, and PCS operation is
time division duplexed, so only the receiver or transmitter is active at any time and a frequency
duplexer is not required.
2
The RFIC operating modes and circuit parameters are MSM-controlled through the proprietary 3-line Serial Bus Interface (SBI). The Application
Programming Interface (API) is used to implement SBI commands. The API is documented in AMSS Software - please see applicable AMSS
Software documentation for details.
CTRL1
CTRL2
CTRL3
EGSM TX
HIGH
HIGH
LOW
DCS/PCS TX
HIGH
LOW
LOW
EGSM RX
LOW
LOW
HIGH
DCS RX
LOW
HIGH
HIGH
PCS RX
LOW
HIGH
LOW
UMTS 1
HIGH
LOW
HIGH
UMTS 2
HIGH
HIGH
HIGH
FRONT END MODULE LOGIC
Table 1.1 Front End Module Control logic
