Only For Training And Service Purposes - LG KP330 Service Manual

3. TECHNICAL BRIEF
shared downconverter. 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 is 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 an interface
shared with GSM Rx to the MSM IC. The UMTS baseband outputs are turned off when the
RTR6285/6280 is downconverting GSM signals and turned on when the UMTS is operating.
The RTR6285/6280 UMTS differential input paths stay on-chip; off-chip interstage filtering is
not required. Other than this, the architecture is similar to the single-ended inputs.
3.1.2 Transmit signal paths
The RTR6285/6280 transmit includes four transmit signal paths (two high bands and two low
bands) supporting multi-bands and multi-modes GSM/GPRS/EDGE polar transmit and
WCDMA/HSDPA transmit architectures.
The transmit path begins with differential baseband signals (I and Q) from the MSM device.
These analog input signals are buffered, filtered by low-path filter, corrected for DC offsets,
amplified, and then applied to the quadrature upconverter mixers.
The upconverter outputs are amplified by multiple variable gain stages that provide transmit
AGC control. SSBI is used to do the gain control. The specified driver amplifier output level is
achieved while supporting the GSM/EDGE and UMTS transmit standard's requirements for
GSM ORFS, carrier and image suppression, WCDMA ACLR, spurious emissions, Rx-band
noise, and so forth.
These upconverters translate the polar GMSK-modulated or 8-PSK modulated baseband PM
signals and/or WCDMA baseband signals directly to the RF signals, which are filtered and
feed into the GSM/EDGE polar PA and/or WCDMA PA. The WCDMA TX power is coupled
back to the RTR6285/6280 internal power detector input pin, PWD_DET_IN, using a coupler
for power measurement.
LGE Internal Use Only
KP330 Operational Description
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Only for training and service purposes