Service Manual
148
t different frequencies.
other is TX FGU providing carrier and exciter signal for the TX system. They work simultaneously, but
are locked a
Both RX FGU and TX FGU mainly consist of a reference crystal oscillator, a PLL, a VCO and a buffer
amplifier. The PLL data is configured via OMAP. See the following figure:
DC_offset
OMAP
LPF
MCSI
MCBSP
LD/
REF
19.2MHz
DAC
MOD_H
Sky72310
MOD_H
VCO1
VCO2
TX PA
Q106
Q105
Q108
BPF
Figure 10-4 Block Diagram of Transmitter
Figure 10-5 Block Diagram of Receiver
utput by the digital-to-analog
converter, so as to ensure frequency accuracy.
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 o
PLL IC
The PLL is a fractional frequency divider (SKY72310), which consists of the pre-divider, programmable
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