Gsm Mode - LG TU550 Service Manual

3.2 GSM Mode

3.2.1 GSM Receiver
The Dual-mode TU550's receiver functions are split between the three RFICs as follows:
• UMTS-850,1900 operation uses the RFL6202 LNA and RFR6202 Receiver ICs to implement the
receive signal path, accepting an RF input and delivering analog baseband outputs (I and Q).
• GSM-850, GSM-900, DCS-1800, and PCS-1900 modes both use the RTR6250 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
parameters.
RF Front end consists of antenna, antenna switch module(CXG1198AEQ), and three RX saw
filters(GSM850, GSM900, DCS and PCS). The antenna switch module allows multiple operating
bands and modes to share the same antenna. In TU550, a common antenna connects to one of eight
paths: 1) UMTS-850 Rx/Tx, 2) UMTS-1900 Rx/Tx, 3) GSM-850 Rx, 4) GSM-900 Rx, 5) GSM-850
GSM-900 Tx, (Low Band Tx's share the same path) 6) DCS-1800 Rx, and 7) DCS-1800,PCS-1900
Tx(High Band Tx's share the same path), 8) PCS-1900 Rx. UMTS operation requires simultaneous
reception and transmission, so the UMTS Rx/Tx connection is routed to a duplexer that separates
receive and transmit signals. GSM850/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.
GSM850/GSM900 TX
DCS/PCS TX
GSM 850 RX
UMTS 850
DCS RX
PCS RX
UMTS 1900
GSM 900
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.
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
IN_A
HIGH
HIGH
LOW
HIGH
LOW
LOW
HIGH
LOW
Table 3.2.1 Antenna Switch Module Control logic
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3. TECHNICAL BRIEF
IN_B IN_C
HIGH LOW
LOW LOW
HIGH LOW
LOW HIGH
HIGH HIGH
LOW HIGH
HIGH HIGH
LOW LOW
LGE Internal Use Only
2 -controlled