In-line piece-wise linear desynchronizer
First Claim
1. A digital desynchronizer for smoothing phase jumps caused by pointer changes of a first signal operating in a first format mapped into a signal operating in a second format comprising:
- A) digital elastic store means for generating a digital elastic store position detection output signal (FJTR), said means having means for receiving the write address and read address associated with the signal operating in the first format, as well as an input for receipt of a threshold signal which in turn is a function in part of the digital elastic store position detection output signal;
B) digital frame jitter filter means for generating a digital frame induced jitter filter output signal (DELTA) having an input connected to the elastic store position output signal (FJTR), said DELTA output signal being linear and proportional to the elastic store position output signal, said digital frame induced jitter filtering means also having means for generating said threshold signal, wherein said threshold signal is a function of the elastic store output signal (FJTR);
C) digital leak filter means connected to the DELTA output, for generating a digital leak rate filter output signal (VCO), said VCO signal being proportional to the desired transmission frequency of the signal in said first format;
D) digital VCO means connected to the VCO signal, for generating a clock signal operating at a frequency of the second format; and
E) means, connected to the clock signal, for generating said read address associated with the signal operating in the first format.
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Accused Products
Abstract
An in-line piece-wise linear desynchronizer eliminates the need for very low bandwidth analog, phase lock loops to smooth phase jumps caused by pointer changes such as those associated with a DS-1 signal mapped into a SONET VT 1.5 payload. The desynchronizer comprises a digital elastic store position detection circuit, a digital frame induced jitter filter, a digital leak rate filter, and a digital frequency synthesizer (VCO). The magnitude of the jitter can be reduced to any level by adjusting the digital VCO resolution and digital leak rate filter time constant. The desynchronizer produces a digitally synthesized output clock which can then be coupled to an analog/digital phase lock loop for smoothing high frequency jitter in the synthesized output clock, thereby providing an in-line interface function.
31 Citations
7 Claims
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1. A digital desynchronizer for smoothing phase jumps caused by pointer changes of a first signal operating in a first format mapped into a signal operating in a second format comprising:
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A) digital elastic store means for generating a digital elastic store position detection output signal (FJTR), said means having means for receiving the write address and read address associated with the signal operating in the first format, as well as an input for receipt of a threshold signal which in turn is a function in part of the digital elastic store position detection output signal; B) digital frame jitter filter means for generating a digital frame induced jitter filter output signal (DELTA) having an input connected to the elastic store position output signal (FJTR), said DELTA output signal being linear and proportional to the elastic store position output signal, said digital frame induced jitter filtering means also having means for generating said threshold signal, wherein said threshold signal is a function of the elastic store output signal (FJTR); C) digital leak filter means connected to the DELTA output, for generating a digital leak rate filter output signal (VCO), said VCO signal being proportional to the desired transmission frequency of the signal in said first format; D) digital VCO means connected to the VCO signal, for generating a clock signal operating at a frequency of the second format; and E) means, connected to the clock signal, for generating said read address associated with the signal operating in the first format. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification