Wavecrest Corporation

Christopher Kimsal

Jan Brian Wilstrup

Dennis M Petrich

Mark J Emineth

Steven H Ulsund

A system is disclosed for precisely measuring time intervals, used to either characterize or diminish noise components in repetitive waveforms. An interval timer generates a whole number count of cycles in combination with beginning and ending ramps capable of resolving fractions of a cycle, to accurately register the time interval. Selection logic can be implemented to time either single periods or spans of multiple consecutive periods of the waveforms. Multiple time measurements are arranged in sets, each set corresponding to a different span of &ldquo;N&rdquo; consecutive periods over a range of values for N. A variance of each set is generated, and an array of variance vs N provides a function having properties of an auto-correlation function. Instrument jitter can be reduced based on measurements of period spans rather than individual periods, and is reduced in proportion to the increasing size of the measured span. These techniques are enhanced by random statistical samples, obtained by a dithering of the measurement rate. This also diminishes the impact of aliasing products.

Analysis of noise in repetitive waveforms

A linear ramp generating and control circuit finding particular applicability in a time interval measurement system. The linear ramp circuit includes a hold capacitor which may be linearly discharged during one operating mode of the circuit by coupling a constant current source to the capacitor. The voltage on the hold capacitor is linearly discharged away from a baseline voltage level to a data voltage level which is subsequently passed to an analog-to-digital converter of the time interval measurement system for further processing. The hold capacitor voltage is returned to the baseline voltage level during a recovery mode of circuit operation by a recovery or recharge network. The recharge network may include an active-feedback circuit which implements an approximately second-order voltage response to the hold capacitor during the recovery mode of operation. The circuit may also include a composite amplifier for buffering the hold capacitor voltage level to a circuit output during a hold mode of circuit operation. The effect of this invention is that the errors such as drift, signal noise, and baseline voltage instability can be minimized.

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Chanhassen, MN, United States of America

Christopher Kimsal