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Digital Averager for Periodic Events Distorted by Phase Jitter

IP.com Disclosure Number: IPCOM000078088D
Original Publication Date: 1972-Nov-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Kohler, D: AUTHOR

Abstract

The digital averager shown in the drawing accepts at A input pulses which are periodic but may be distorted by phase jitter, and furnishes at B output pulses at regular intervals which are the average of intervals between input pulses. This averager constitutes a completely digital phase-locked loop.

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Digital Averager for Periodic Events Distorted by Phase Jitter

The digital averager shown in the drawing accepts at A input pulses which are periodic but may be distorted by phase jitter, and furnishes at B output pulses at regular intervals which are the average of intervals between input pulses. This averager constitutes a completely digital phase-locked loop.

Time between an output pulse B and the input pulse A of the next period is measured by counting the cycles of a reference clock in a binary counter. Every second pulse of the output sequence B resets the binary counter, and every second pulse of the input sequence A transfers the current contents of the binary counter through AND gates to a register. A mode select logic ensures that pulses of the input sequence A on one hand and of the output sequence B on the other hand are taken from alternating periods.

An accumulator is used for developing the average value. Each new measurement value appearing in the register is added to the accumulator contents, but for each such addition the current average value is subtracted. The average over 2/N/ measurements is obtained simply by disregarding the last N digits of the accumulator contents.

For start-up one can either begin with an empty accumulator and inhibit the first 2/N/ subtractions, or simply depend on the self-adjusting mechanism which exponentially reaches the average value with a time constant of 2/N/ measurements.

To convert the binary representation o...