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Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
3. TECHNICAL BRIEF
3.2 GSM Mode
3.2.1 GSM Receiver
The Dual-mode KB770’s receiver functions are split between the three RFICs as follows:
■
EGSM-900(GSM900), DCS-1800, and PCS-1900 modes 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 (LMSP4LMA-573TEMP) which includes three
RX saw filters (EGSM-900, DCS-1800 and PCS-1900). The antenna switch module allows multiple
operating bands and modes to share the same antenna. In KB770, a common antenna connects to one of
six paths: 1) UMTS-2100 Rx/Tx, 2) EGSM-900 Rx, 3) EGSM-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.
Table 3.2.1 Antenna Switch Module Control logic
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.
