Service Manual
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cy is generated by the LC resonance loop.
TX FGU mainly consist of a reference crystal oscillator, a PLL, a VCO and a buffer
The 18MHz clock frequen
9.3 Frequency Generation Unit (FGU)
The repeater has two FGUs. One is RX FGU providing the first LO frequency for the RX system; the
other is TX FGU providing carrier and exciter signal for the TX system. They work simultaneously, but
are locked at different frequencies.
Both RX FGU and
amplifier. The PLL data is configured via OMAP. See the following figure:
LPF
DC_offset
OMAP
MCSI
MCBSP
LD/
REF
19.2MHz
DAC
Sky72310
MOD_H
MOD_H
VCO1
VCO2
TX PA
Q106
Q105
Q108
LPF
Figure 9-4 Block Diagram of Transmitter
Figure 9-5 Block Diagram of Receiver
9.3.1 Reference Oscillator
The reference crystal oscillator is a temperature compensated crystal oscillator with a frequency of
19.2MHz. You can control the oscillator by adjusting the DC voltage output by the digital-to-analog
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