Method of and circuit for the measurement of jitter modulation of zero-related digital signals

DETAILED DESCRIPTION I claim: 1.
In a process for measuring a jitter modulation of a digital signal (DS) in which first pulses, which are derived from certain pulse flanks of the jitter-associated digital signal, and second pulses of a jitter free reference clock pulse, which are derived from a bit-clock frequency of the jitter-associated digital signal, are subjected to a phase comparison, whereby one of said first and second pulses starts a linearly rising ramp generator, the other of said first and second pulses determines sampling points of the ramp signal, and sampled valued of the ramp signal are held to form a sampled and held ramp signal, and whereby an alternating component of the sampled and held ramp signal is proportional to the jitter modulation and a direct component of the sampled and held ramp signal establishes a setting value for the generation of the jitter free reference frequency, the improvement which comprises the combination of the following steps: (a) generating the reference clock pulse with a pulse-repetition frequency nf.
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B =f.
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T corresponding to a multiple n of the bit clock frequency f.
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B where n is an integer and dividing each bit clock period with a duration T.
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B =1/nf.
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B is divided into n partial periods each having a duration t=T.
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B /n=1/nf.
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B ; (b) starting the ramp generator (5) upon the application of a release signal once in each bit clock period and p partial periods after the end of that partial period in which appears the predetermined pulse flank of the digital signal (DS), where p=0, 1, 2, .
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<n; (c) forming the ramp length of the sawtooth signal (S3) to be slightly longer than one partial period; (d) forming a sampling pulse (S4) which is delayed with respect to the predetermined pulse flank of the digital signal (DS) by p+1 partial periods; (e) determining a coarse phase value by an ordinal value of that partial period in which the predetermined pulse flank appears and after the passage of p partial periods applying the release signal is applied to the ramp generator (5); and (f) adding an alternating component of the sampled and held ramp signal and the coarse phase value to form the measurement of the jitter modulation