LG KF690 Service Manual page 14

The GSM900, DCS1800, and PCS1900 receive signals are routed to the RTR6235 through band
selection filters and matching networks that transform single-ended 50Ω 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 RTR6235 input
stages include ESM6270-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 filte
circuits include DC offset corrections. The filter outputs are buffered and passed on to the ESM6270
IC for further processing.r
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
[Fig. 3.2] RTR6235 RX feature
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3. TECHNICAL BRIEF
LGE Internal Use Only