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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 KS20’s receiver functions are split between the three RFICs as follows:
• GSM-900, DCS-1800, and PCS-1900 UMTS-2100 modes bot 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, antenna switch module(LSHS-M090U) which includes 3 RX saw
filters(GSM900, DCS and PCS). The antenna switch module allows multiple operating bands and
modes to share the same antenna. In KS20, 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, 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.
ANT_SEL0 ANT_SEL1 ANT_SEL2
GSM 850/GSM 900 TX HIGH HIGH LOW
GSM 1800/GSM 1900 TX HIGH LOW LOW
GSM 850 RX - - -
GSM 900 RX LOW LOW LOW
GSM 1800 RX LOW LOW LOW
GSM 1900 RX LOW LOW HIGH
WCDMA HIGH LOW HIGH
[Table 1.1] Antenna Switch Module Control logic
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