LGE Internal Use Only
Copyright © 2008 LG Electronics. Inc. All right reserved.
Only for training and service purposes
3. TECHNICAL BRIEF
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3.4 LO generation and distribution circuits
The integrated LO generation and distribution circuits are driven by internal VCOs to support various
modes to yield highly flexible quadrature LO outputs that drive all GSM/EDGE and UMTS band
upconverters and downconverters; with the help of these LO generation and distribution circuits, true
zero-IF architecture is employed in all GSM and UMTS band receivers and transmitters to translate the
signal directly from RF to baseband and from baseband to RF.
Two fully functional fractional-N synthesizers, including VCOs and loop filters, are integrated within the
RTR6275 IC. The first synthesizer (PLL1) creates the transceiver LOs that support the UMTS 2100
transmitter, and all four GSM band receivers and transmitters including: GSM900, DCS1800, and
PCS1900. The second synthesizer (PLL2) provides the LO for the UMTS 2100 receiver. An external
TCXO input signal is required to provide the synthesizer frequency reference to which the PLL is
phase and frequency locked. The RTR6275 IC integrates most of PLL loop filter components on-chip
except two off-chip loop filter series capacitors, and significantly reduces off-chip component
requirement. With the integrated fractional-N PLL synthesizers, the RTR6275 has the advantages of
more flexible loop bandwidth control, fast lock time, and low-integrated phase error
Содержание KF700
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