LG U8138 Service Manual page 77

3. TECHNICAL BRIEF
D. VCO Block
The VCOs are fully integrated balanced LC oscillators with on-chip resonators. The receive VCOs run
on double frequency.
Different frequency ranges can be selected in the VCOs for GSM/DCS band operation.
The VCOs are supplied from a separated external voltage regulator to avoid frequency pushing and up
conversion of low frequency noise. A separate ground pin is also used as varactor ground reference to
prevent DC voltage drop changes from affecting the VCO frequency.
Figure 3-5 shows a block diagram of the VCO block.
Figure 3-5. Block diagram of the VCO part.
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