The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 05, 1998
Filed:
Aug. 11, 1995
Marc L Smith, Sterling, MA (US);
Fadi H Daou, Milton, MA (US);
CenRad, Inc., Concord, MA (US);
Abstract
To measure various frequency components of the jitter of the deviation of the transition times in a signal on a signal line (44) from nominal bit times, a sampler (40) samples the signal at a rate high enough to determine the transition time with the required resolution. By employing a differentiator (60), test circuitry (FIG. 3B) can detect not only zero crossings but all digital-level transitions. The timings of the maxima of the differentiator output are applied to a Fourier-transform unit (76) that computes jitter-frequency components from a resultant sequence of deviations of the maxima from nominal transition times. Although computation of the lowest jitter-frequency components is necessarily based on a sequence that extends over a correspondingly long signal record, the input of a memory (48) that receives the raw samples from which those transition-time deviations are computed is so gated that the memory (48) receives only infrequently occurring bursts of the sampler's high-sample-rate output when the lower jitter frequencies are to be measured. A memory (48) of only moderate size can therefore be employed despite the necessarily high sample rate and necessarily long record duration.