Analog phase locked loop
AssigneeMitel Corporation
InventorsPeter Gillingham, Jan H. Erkku
Life of this patent
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Abstract
A phase locked loop for synchronizing a local digital signal with an incoming data signal is described. Parallel phase and frequency detectors compare the local and incoming signals and generate control pulse signals for controlling the frequency of a voltage controlled oscillator which generates the local digital signal. Logic circuitry is included in both the phase and frequency detectors for adjusting the generated control pulse signals in the event of detection of elongated pulse widths of the incoming data signal, indicating one of either an absence of incoming data signal or a bipolar violation in the event the data signals are ASI encoded. The phase locked loop is characterized by quick pull-in time, large pull-in frequency range, accurate clocking and low cost.
Claims14
A phase locked loop for synchronizing a local digital signal with a remote digital signal, comprised of:
- (a) first means for receiving and comparing said local and remote digital signals, and upwardly adjusting the frequency of said local signal in the event the local signal frequency is less than the remote signal frequency, and downwardly adjusting the frequency of said local signal in the event the local signal frequency is greater than the remote signal frequency,
- (b) second means for receiving and comparing said local and remote signals, and upwardly adjusting the frequency of said local signal in the event the local signal phase lags the remote signal phase, and downwardly adjusting the frequency of said local signal in the event the local signal phase leads the remote signal phase, and
- (c) means for detecting elongated pulse widths of said remote digital signal and upwardly adjusting the frequency of said local signal in response thereto, for counteracting downward adjustment of the local signal frequency by said first and second means in response to detection of said elongated remote signal pulse widths,
- whereby said local and remote signals are phase and frequency locked regardless of pulse width anomalies of said remote signal.
Dependencies are inferred from the claim text.