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Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
LGE Internal Use Only
3. TECHNICAL BRIEF
3.3 UMTS Mode
3.3.1 Receiver
The UMTS duplexer receiver output is routed to LNA circuits within the RFR6275 device.
UMTS LNA circuits(one for low-band UMTS and one for high-ban UMTS path) separated from all other
receive functions contained within the RFR6275 receiver IC to improve mixer LO to RF isolation a critical
parameter in the ZIF architecture. Isolation is further improved using high-reverse isolation circuits into the
LNA designes.
The LNA gains are stepped via API control. The IC operating mode and LNA bias currents re-
automatically adjusted via software to minimize DC power consumption.
The UMTS Rx input is provided with an on-chip LNA that amplifies the signal before a second stage filter
that provides differential downconverter. This second stage input is configured differentially to optimize
second-order 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 RTR6275 is
downconverting GSM signals and on when the UMTS is operating.