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    Frequency demodulator for noise threshold extension
    1.
    发明授权
    Frequency demodulator for noise threshold extension 失效
    用于噪声阈值扩展的频率解调器

    公开(公告)号：US3611169A

    公开(公告)日：1971-10-05

    申请号：US3611169D

    申请日：1968-08-15

    申请人： POLYTECHNIC INST BROOKLYN

    发明人： HESS DONALD T ,  CLARKE KENNETH K

    IPC分类号： H03D1/20 ,  H03D3/00 ,  H03D5/00

    CPC分类号： H03D1/20 ,  H03D3/001 ,  H03D5/00

    摘要： Described herein is a frequency modulation signal demodulation system which utilizes the amplitude modulation information inherent in a noise-corrupted frequency modulation carrier to control the parameters of a feedback loop, through which the demodulated FM information is passed, during the occurrence of large noise-induced, pulselike disturbances in the demodulated frequency modulation information. This function is performed by a circuit configuration which includes an amplitude modulation demodulator and a frequency modulation demodulator supplied in parallel from the input to the system for deriving information signals which are respective functions of the instantaneous envelope information and the instantaneous frequency modulation information. The control of the parameters of the feedback loop may be accomplished by the instantaneous envelope information directly or by the envelope information on which some process has been performed. The description also refers to the fact that the envelope detector may have linear or nonlinear characteristics. One way in which the envelope information may be processed is by a nonlinear quantizer followed by a time delay circuit which is interposed between the envelope demodulator and the means for controlling the feedback loop which modifies the frequency modulation information signals. The final output signals may be taken from the output of the feedback loop through a low-pass filter. If desired, an equalizing filter may also be interposed between the output of the feedback loop and the final low-pass filter.