Umts Mode - LG CT815 Service Manual

3. TECHNICAL BRIEF

3.3 UMTS MODE

3.3.1 UMTS RECEIVER
The UMTS duplexer receiver output is routed to LNA circuits within the RTR6285 device as shown in
Figure .3-4. The UMTS RX input is provided with an on-chip LNA that amplifies the signal before a
second stage filter that provides differential downconverter as shown in Figure 1-5. This second stage
input is configured differentially to optimize second-order intermodulation and common mode rejection
performance. The gain of the UMTS front end amplifier and the UMTS second stage differential
amplifier are adjustable, under MSM control, to extend the dynamic range of the receivers. The second
stage UMTS RX amplifiers drive the RF ports of the quadrature RF-to-baseband downconverters. The
downconverted UMTS RX baseband outputs are routed to lowpass filters having passband and
stopband characteristics suitable for UMTS RX processing. These filter circuits allow DC offset
corrections, and their differential outputs are buffered to interface shared with GSM RX to the MSM IC.
The UMTS baseband outputs are turned off when the RTR6285 is downconverting GSM signals and on
when the UMTS is operating.
LGE Internal Use Only
[Figure 3-4] UMTS Receiver Inputs Topologies
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