发明公开
- 专利标题: Automatic frequency control
- 专利标题(中): 自动售货机
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申请号: EP89104874.6申请日: 1989-03-18
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公开(公告)号: EP0343336A2公开(公告)日: 1989-11-29
- 发明人: Marz, Daniel J. , Schilling, John D.
- 申请人: GENERAL INSTRUMENT CORPORATION OF DELAWARE
- 申请人地址: 181 West Madison Street Chicago, Illinois 60602 US
- 专利权人: GENERAL INSTRUMENT CORPORATION OF DELAWARE
- 当前专利权人: GENERAL INSTRUMENT CORPORATION OF DELAWARE
- 当前专利权人地址: 181 West Madison Street Chicago, Illinois 60602 US
- 代理机构: Hoeger, Stellrecht & Partner
- 优先权: US197616 19880523
- 主分类号: H03J7/04
- IPC分类号: H03J7/04 ; H04N5/50
摘要:
An automatic frequency control tracks a television signal before and after a period of interruption. The automatic frequency control comprises a voltage controlled feedback loop including a voltage controlled local oscillator (18) and a mixer (20) for mixing the output of the oscillator (18) with the TV signal. The output of the mixer (20) is filtered to remove unwanted components of the mixed signal and to equalize sidebands of the television signal. The output of the filter (24) is supplied to a detector (30) which is tuned to a component of the television signal, and produces a voltage corresponding to the frequency of the component. The output of the detector (30) is supplied to the voltage control input of the local oscillator (18) to track the television signal component. Circuitry (71, 72) automatically senses the absence of the TV signal component from the mixer (20), and automatically applies a reference voltage (V R ) to the voltage control input of the oscillator (18) when the TV signal component is absent. The detector (30) is operative to detect the television signal component following the application of reference voltage (V R to the oscillator so that when the television signal returns, the detector (30) is capable of tracking it.
公开/授权文献
- EP0343336B2 Automatic frequency control 公开/授权日:1999-12-15
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