Noise reduction circuits
First Claim
1. A clock restoration circuit for reducing noise in an input pulse train consisting of pulses having a nominal periodicity and from which one or more pulses is missing, the clock restoration circuit including,DC removal means for removing a DC level from the input pulse train, integrator means for integrating the input pulse train after said DC level has been removed therefrom by the DC removal means, detection means for receiving an output from the integrator means and for detecting from said output a missing pulse in the input pulse train, pulse generating means responsive to the detection means for inserting into the input pulse train an additional pulse delayed with respect to said missing pulse detected by the detection means and output means for generating an output pulse train from said output from the integrator means.
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Abstract
A noise reduction circuit useful as a clock restoration circuit includes a DC removal circuit for removing a DC level from an input pulse train, an integrator for integrating the input pulse train after a DC level has been removed, a comparator for comparing the integrator output with a threshold value (Vmp) to detect for a missing pulse, a pulse generator inserting into the input pulse train an additional pulse delayed with respect to any missing pulse, and an output circuit for generating an output pulse train from the integrator output.
23 Citations
39 Claims
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1. A clock restoration circuit for reducing noise in an input pulse train consisting of pulses having a nominal periodicity and from which one or more pulses is missing, the clock restoration circuit including,
DC removal means for removing a DC level from the input pulse train, integrator means for integrating the input pulse train after said DC level has been removed therefrom by the DC removal means, detection means for receiving an output from the integrator means and for detecting from said output a missing pulse in the input pulse train, pulse generating means responsive to the detection means for inserting into the input pulse train an additional pulse delayed with respect to said missing pulse detected by the detection means and output means for generating an output pulse train from said output from the integrator means.
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17. A phase noise reduction circuit for reducing phase noise in an input pulse train consisting of pulses having a nominal frequency f, the phase noise reduction circuit comprising,
means for deriving a first pulse train from the input pulse train, the first pulse train consisting of pulses triggered by positive-going transitions of the pulses forming the input pulse train, means for deriving a second pulse train from the input pulse train, the second pulse train consisting of pulses triggered by negative-going transitions of the pulses forming the input pulse train, combining means for combining the first and second pulse trains to form a combined pulse train, DC removal means for removing a DC level from the combined pulse train, integrator means for integrating the combined pulse train after said DC level has been removed from the combined pulse train by the DC removal means to produce an integrated output and processing means for deriving from the integrated output an output pulse train at said nominal frequency f.
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20. A clock restoration circuit for reducing noise in an input pulse train consisting of pulses which have a nominal periodicity and amongst which one or more spurious additional pulse is present, the clock restoration circuit including,
DC removal means for removing a DC level from the input pulse train, integrator means for integrating the input pulse train after said DC level has been removed from the input pulse train by the DC removal means, pulse deletion means for deleting a said spurious additional pulse from the input pulse train, said pulse deletion means comprising pulse generating means for receiving an output from said integrator means and for generating blanking pulses in response to said output and means for combining said blanking pulses with said pulses of said input pulse train to delete said one or more spurious additional pulse and output means for deriving an output pulse train from said output from the integrator means.
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33. A circuit for reducing phase noise in an input pulse train consisting of pulses having a nominal periodicity, the circuit including DC removal means for removing a DC level from the input pulse train,
integrator means for integrating the input pulse train after said DC level has been removed from said input pulse train by the DC removal means and at least two detection means for producing different output pulse trains in response to an output from the integrator means and to respectively different reference signals whereby each said output pulse train contains periodic transitions having a respective phase relationship to transitions of the input pulse train dependent on the corresponding said reference signal.
Specification