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LGE Internal Use Only
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
3. TECHNICAL BRIEF
The GSM900, DCS1800, and PCS1900 receiver inputs of RTR6275 are connected directly to the
transceiver front-end circuits(filters and antenna switch module). GSM900, DCS1800, and
PCS1900 receiver inputs use differential configurations to improve common-mode rejection and
second-order non-linearity performance. The balance between the complementary signals is critical
and must be maintained from the RF filter outputs all the way into the IC pins.
Since GSM900, DCS1800, and PCS1900 signals are time-division duplex (the handset can only
receive or transmit at one time), switches are used to separate Rx and Tx signals in place of
frequency duplexers – this is accomplished in the switch module.
The GSM900, DCS1800, and PCS1900 receive signals are routed to the RTR6275 through band
selection filters and matching networks that transform single-ended 50W
sources to differential
impedances optimized for gain and noise figure. The RTR input uses a differential configuration to
improve second-order inter-modulation and common mode rejection performance. The RTR6275
input stages include MSM-controlled gain adjustments that maximize receiver dynamic range.
The amplifier outputs drive the RF ports of the quadrature RF-to-baseband downconverters. The
downconverted baseband outputs are multiplexed and routed to lowpass filters (one I and one Q)
having passband and stopband characteristics suitable for GMSK or 8-PSK processing. These filter
circuits include DC offset corrections. The filter outputs are buffered and passed on to the
MSM6280 IC for further processing.
