3. TECHNICAL BRIEF
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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.
[Figure 1-4] UMTS Receiver Inputs Topologies