发明名称 |
Automatic frequency control circuit |
摘要 |
An AFC circuit stabilizes the frequency of an intermediate frequency signal to be applied to a demodulation circuit. A frequency conversion circuit responds to a local oscillation signal generated from a voltage-controlled oscillation circuit to convert the frequency of a digital modulation signal and applies the converted frequency to the demodulation circuit. A carrier reproduction circuit in the demodulation circuit reproduces the carrier of the intermediate frequency signal to output a synchronizing detection signal. The frequency of the reproduced carrier is frequency-divided by a frequency dividing circuit. A frequency division output thereof is counted by a counter for a definite period. Data is outputted from a microprocessor in response to a count output of the counter and the synchronizing detection signal, and the data is then converted into an AFC voltage by a D/A converter. The converted voltage is supplied as a control voltage to the voltage-controlled oscillation circuit. A stable intermediate frequency signal can be obtained by frequency-dividing the frequency of the carrier and counting the frequency division output thereof.
|
申请公布号 |
US5289506(A) |
申请公布日期 |
1994.02.22 |
申请号 |
US19920842540 |
申请日期 |
1992.02.27 |
申请人 |
SHARP KABUSHIKI KAISHA |
发明人 |
KITAYAMA, TAKAMITSU;MIYAZAKI, MASAO;OHTA, TOMOZO;CHIHARA, TAKAHIRO |
分类号 |
H03J7/06;H04L27/00;H04L27/227;(IPC1-7):H04L27/06 |
主分类号 |
H03J7/06 |
代理机构 |
|
代理人 |
|
主权项 |
|
地址 |
|