LG KE990 Service Manual - Page 17
Fig 3.2.2] RTR6235 RX feature
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3. TECHNICAL BRIEF The EGSM900, DCS1800, and PCS1900 receive signals are routed to the RTR6235 through band selection filters and matching networks that transform single-ended 50-Ω•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 ESMcontrolled 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 ESM6270 IC for further processing LGE Internal Use Only [Fig 3.2.2] RTR6235 RX feature - 18 - Copyright © 2008 LG Electronics. Inc. All right reserved. Only for training and service purposes