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F/S TUNING SYSTEM DESCRIPTION
The C-003 Frequency Synthesizer Tuning System is similar to previous PLL
(Phase Locked Loop) systems described in earlier training manuals. The
primary difference between this system and previous systems is that much of
the system has been integrated into a single IC and included in the Tuner.
The advantages of this new synthesizer IC tuner package include: single IC
chip and a smaller circuit board due to synthesizer integration, reduced
control lines are required from the CPU (2 versus 3), and reduced power
consumption, RF radiation and interference.
A block diagram comparison of the previous and present system is shown
below.
In operation, the tuner is precisely adjusted to the frequency of the channel
selected by phase comparing (after frequency division) the tuner local
oscillator frequency with a crystal controlled oscillator reference frequency in
the MIX-OSC/PLL IC (CXA3135AN). Any deviation of the local oscillator
frequency from the correct channel frequency will result in an output from the
phase detector.
The output from the phase detector is amplified and used to control the exact
frequency of the tuner local oscillator.
Channel selection is accomplished by control pulses from the CPU which
determine the frequency division ratio of the programmable divider in the MIX-
OSC/PLL IC.
Previous Synthesizer Tuning Systems
AVM-2780G Synthesizer Tuning System
CPU
TUNER
DATA
CLOCK
CPU
TUNER
DATA
CLOCK
ENABLE
