Browse Prior Art Database

Word At A Time A D Converter

IP.com Disclosure Number: IPCOM000090959D
Original Publication Date: 1969-Aug-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Frei, AH: AUTHOR

Abstract

A steady-state oscillatory pattern representing values of the Stiglitz-Gray code and sampled pulse phase-modulated analog values are superimposed in couplers. A number of n threshold circuits detect these and produce n output digits. Thus, analog values are converted to digital representation by this word-at-a-time converter with only n discriminating elements. The characteristic periodicity of the pattern is shown in this table of digital representations known as the Stiglitz-Gray code: Period 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 in bits 16 0 0 0 0 0 0 0 0 L L L L L L L L 16 0 0 0 0 L L L L L L L L 0 0 0 0 8 0 0 L L L L 0 0 0 0 L L L L 0 0 4 0 L L 0 0 L L 0 0 L L 0 0 L L 0.

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Word At A Time A D Converter

A steady-state oscillatory pattern representing values of the Stiglitz-Gray code and sampled pulse phase-modulated analog values are superimposed in couplers. A number of n threshold circuits detect these and produce n output digits. Thus, analog values are converted to digital representation by this word- at-a-time converter with only n discriminating elements. The characteristic periodicity of the pattern is shown in this table of digital representations known as the Stiglitz-Gray code: Period 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 in bits 16 0 0 0 0 0 0 0 0 L L L L L L L L 16 0 0 0 0 L L L L L L L L 0 0 0 0 8 0 0 L L L L 0 0 0 0 L L L L 0 0 4 0 L L 0 0 L L 0 0 L L 0 0 L L 0.

All sixteen bits represent a sampling period of tau s = 1/fs, fs being the clock frequency. A harmonic square-wave generator fed by the clock produces the above pattern. The waves follow down n lines. Appropriate delays provide for correct relative phasing. A sample and hold circuit produces a staircase DC voltage which in turn drives the pulse phase modulator. Its output pulse is delayed by tau which is proportional to the sampled analog voltage. Superposition with the square-wave pattern occurs in the couplers represented by diamond-shaped symbols. Arrows indicate the direction of signal flow.

In the example, all but the third bistable circuit flip to the upper level, thus indicating the Gray code LLOL. Reset of the bistable circuits occurs shortly before the...