Umts Mode - LG -P500 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 1-4. 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 secondorder intermodulation and common mode rejection
performance. The gain of the UMTS frontend 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 1-4] UMTS Receiver Inputs Topologies
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