| 摘要 |
A frequency detector and method for use in timing and carrier recovery applications. In a timing recovery application, the circuit includes means for generating a variable frequency periodic clock signal corresponding to an input data signal, means for determining whether successive data transitions of the data signal occur during first and second predetermined portions of successive cycles of the clock signal and means for changing the frequency of the clock signal when successive data transitions occur during different ones of the predetermined portions. For carrier recovery applications, the circuit includes means responsive to an input signal for generating a timing recovery signal, means for generating a local carrier signal having in-phase and quadrature axis components, means responsive to the local carrier signal and to the input signal for forming a baseband signal having in-phase and quadrature axis components, means responsive to the timing recovery signal for sampling the baseband signal at timing intervals corresponding to the timing recovery signal thereby forming a sample baseband signal, means for determining when the sample baseband signal occurs within a predetermined region of the in-phase axis or quadrature axis and means for changing the frequency of the carrier signal if successive samples are on opposite sides of the in-phase axis or quadrature axis.
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