Title:
AUTOMATIC FREQUENCY CONTROL CIRCUIT
Document Type and Number:
Japanese Patent JP2570124
Kind Code:
B2
Abstract:
PURPOSE: To obtain a stable AFC operation by providing a temperature compensation circuit absorbing a fluctuation of an AFC control voltage accompanied with a temperature fluctuation to an AFC voltage control circuit comparing an AFC voltage and a reference voltage to provide an AFC control voltage.
CONSTITUTION: An AFC comparator circuit 10 compares an AFC voltage VAFC with a reference voltage VREF from a reference voltage generating circuit 8 and obtains a difference and it is used to control an oscillating frequency of a local oscillator 6. When a fluctuation takes place in a voltage VAFC outputted from a demodulator 4 due to the temperature fluctuation, a temperature compensation circuit 9 provided to an AFC voltage control circuit 7 changes the voltage VREF, based on the temperature fluctuation. For example, when the voltage VAFC is increased by the temperature rise of the demodulator 4, the compensation to increase the voltage VREF by the same level as the fluctuation in the voltage VAFC is implemented to provide the output of a voltage VREF, Thus, the difference voltage of the both, that is, the AFC control voltage VCNT is kept constant regardless in the increase in the voltage VAFC to attain stable AFC control.
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Inventors:
Tomomi Iwasaki
Application Number:
JP20208493A
Publication Date:
January 08, 1997
Filing Date:
July 23, 1993
Export Citation:
Assignee:
NEC
International Classes:
H03L1/02; H03L7/06; (IPC1-7): H03L7/06; H03L1/02
Domestic Patent References:
| JP6231205A | ||||
| JP1103027A | ||||
| JP622836Y2 |
Attorney, Agent or Firm:
Suzuki Akio