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    Television tuning system with provisions for receiving RF carrier at nonstandard frequency
    5.
    发明授权
    Television tuning system with provisions for receiving RF carrier at nonstandard frequency 失效
    电视调谐系统，用于以非标准频率接收RF载波

    公开(公告)号：US4031549A

    公开(公告)日：1977-06-21

    申请号：US688521

    申请日：1976-05-21

    申请人： Robert Morgan Rast ,  Charles Martin Wine ,  John Goodchilde Norie Henderson

    发明人： Robert Morgan Rast ,  Charles Martin Wine ,  John Goodchilde Norie Henderson

    IPC分类号： H03J5/02 ,  H03J7/06 ,  H04N5/50 ,  H04B1/26

    CPC分类号： H03J7/065 ,  H03J5/0272 ,  Y10S331/02

    摘要： A tuning system for a television receiver includes a phase locked loop for tuning a local oscillator to the nominal local oscillator frequencies required to tune the receiver to RF carriers at standard broadcast frequencies allocated to the various channels a viewer may select. The tuning system also includes an automatic fine tuning (AFT) frequency discriminator for tuning the local oscillator to minimize any deviation between the frequency of an actual picture carrier and the nominal picture carrier frequency. If the receiver is coupled to a television distribution system which provides RF carriers having nonstandard frequencies arbitrarily near respective ones of the standard broadcast frequencies, when the phase locked loop has achieved lock at a nominal frequency, a mode control unit selectively couples the discriminator and a frequency drift control circuit to the local oscillator. If the frequency of the local oscillator drifts more than a predetermined offset from the frequency synthesized under phase locked loop control because no carrier has been detected by the discriminator, discriminator and drift control are terminated so that the receiver will not be tuned to an undesired carrier such as, for example, the lower adjacent channel sound carrier, and phase locked loop control is reinitiated to synthesize a local oscillator signal having a frequency different from the frequency of the originally synthesized local oscillator signal by a predetermined amount. After the phase locked loop is locked at the new frequency, discriminator control is again initiated.

    摘要翻译： 用于电视接收机的调谐系统包括用于将本地振荡器调谐到分配给观众可以选择的各种频道的标准广播频率将接收机调谐到RF载波所需的标称本地振荡器频率的锁相环。 调谐系统还包括用于调谐本地振荡器的自动微调（AFT）鉴频器，以最小化实际图像载波的频率与标称图像载波频率之间的任何偏差。 如果接收机耦合到电视分配系统，该电视分配系统提供具有任意接近标准广播频率的相应标准广播频率的非标准频率的RF载波，则当锁相环已经达到标称频率的锁定时，模式控制单元选择性地将鉴别器和 频率漂移控制电路到本地振荡器。 如果本地振荡器的频率漂移超过在锁相环控制下合成的频率的预定偏移，因为鉴别器没有检测到载波，则终止鉴频器和漂移控制，使得接收机不会被调谐到不需要的载波 例如下相邻声道声音载波，并且重新启动锁相环控制，以将具有与原始合成的本地振荡器信号的频率不同的频率的本地振荡器信号合成预定量。 锁相环锁定在新频率之后，再次启动鉴频器控制。