Time jitter determining apparatus
First Claim
1. Apparatus for determining time jitter of a clock signal of period Tb, recovered from a received data signal, comprising:
- means for applying the clock signal to first and second signal paths;
signal delay means for delaying the signals in the signal paths relative to one another by a variable delay factor;
logic means coupled to the first and second signal paths for detecting coincidence of the relatively delayed clock signals, anddetector means coupled to the logic means for indicating the coincidence rate of the relatively delayed clock signals, as the delay is varied, whereby peak to peak time jitter is half of the relative shift of the delay between the point of minimum coincidence and the point of maximum coincidence.
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Abstract
The jitter determining apparatus uses only a jittery clock signal of period Tb recovered from the received data signal to determine peak to peak jitter Jpp and jitter distribution. The apparatus includes an AND gate having a pair of inputs. The inputs are coupled to a first signal which is the jittery clock signal delayed by a fixed amount nTb where n is preferably greater than 5, and to a second signal which is a jittery pulse signal generated from the jittery clock signal. The second signal is also controllably delayed by a factor greater than twice the jitter Jpp. The AND gate produces output pulses when coincidence occurs between the two signals as the delay of the second signal is selectively varied. A counter counts the pulses for each selected delay position and thus provides the peak to peak time jitter Jpp of the clock signal.
142 Citations
14 Claims
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1. Apparatus for determining time jitter of a clock signal of period Tb, recovered from a received data signal, comprising:
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means for applying the clock signal to first and second signal paths; signal delay means for delaying the signals in the signal paths relative to one another by a variable delay factor; logic means coupled to the first and second signal paths for detecting coincidence of the relatively delayed clock signals, and detector means coupled to the logic means for indicating the coincidence rate of the relatively delayed clock signals, as the delay is varied, whereby peak to peak time jitter is half of the relative shift of the delay between the point of minimum coincidence and the point of maximum coincidence. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. Apparatus for determining time jitter of a clock signal of period Tb, recovered from a received data signal, comprising:
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means for applying the clock signal to first and second signal paths; signal delay means for delaying the signals in the signal paths relative to one another by a variable delay factor; AND gate means having one input coupled to the signal in the first signal path and one input coupled to the signal in the second signal path; and counter means coupled to the AND gate means for counting the coincidence rate of pulses received from the AND gate, as the delay is varied. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification