LG U8110 Service Manual page 89

3. TECHNICAL BRIEF
A. IF PLL
The IF LO frequency synthesis comprises the four following parts:
- Input buffer: A 13MHz input buffer with DC-biasing provided at source.
- VCO: Operating on 1.52GHz which is 4times the TX-IF frequency (380MHz) and 8 times the RX-IF
(190MHz), this is a fully integrated balanced LC oscillator with on-chip resonator. On-chip varactor
are used to tune the VCO frequency.
- Prescaler
- Phase-detector with charge pump
For maintaining check on the VCO center frequency, the tuning voltage is set to Vcc/2. External DC
blocking capacitors must be used on the IFLO/IFLOBAR signals.
Figure 3-15. Block Diagram of Frequency Synthesizer Part(IF PLL).
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