Gsm Mode - LG U990 Service Manual

3.2 GSM Mode

3.2.1 GSM Receiver
The Dual-mode U990's receiver functions are split between the three RFICs as follows:
• GSM-900, DCS-1800, PCS-1900 and UMTS-2100 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 SBI2-
controlled parameters.
RF Front end consists of antenna, antenna switch module (LSHS-M090UH) which includes three RX
saw filters (GSM-900, DCS-1800 and PCS-1900). The antenna switch module allows multiple
operating bands and modes to share the same antenna. In U990, a common antenna connects to one
of six paths: 1) UMTS-2100 Rx/Tx, 2) GSM-900 Rx, 3) GSM-900 Tx, 4) DCS-1800 Rx, and 5) DCS-
1800, PCS-1900 Tx(High Band Tx's share the same path), 6) 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. GSM900, DCS1800, and PCS1900 operation is time division
duplexed, so only the receiver or transmitter is active at any time and a frequency duplexer is not
required.
Control Logic (L : 0 ~ 0.1V, H : 2.6 ~ 2.8V)
GSM900 Tx
DCS1800/PCS1900 Tx
UMTS Tx/Rx
GSM 900 Rx
DCS 1800 Rx
PCS 1900 Rx
L/H : L and H are acceptable
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
Vc3
L
L
H
L
H
L
[Table 1.1] Antenna Switch Module Control logic
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3. TECHNICAL BRIEF
Vc2 Vc1
H H
L H
L H
L/H L
L/H L
L/H L
Vdd
H
H
H
H
H
H
LGE Internal Use Only