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Mathematical Technique for Compensating for Waveform Distortion

IP.com Disclosure Number: IPCOM000109635D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 119K

Publishing Venue

IBM

Related People

Calabrese, GM: AUTHOR [+2]

Abstract

This article describes a mathematical technique for analyzing digitized waveforms and applying certain "correction factors". This technique was developed for the testing and qualification of Active Board Channel Maintenance (ABCM) design used in the ES/9000* System ABCM refers to "Hot Plugging" channel cards in an active board, without disturbing the operation of neighboring cards. An overview of the test strategy is described in "Active Board Channel Maintenance Noise Simulation and Test Method," IBM Technical Disclosure Bulletin 35, 4A, 398-399 (September 1992, this issue).

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Mathematical Technique for Compensating for Waveform Distortion

       This article describes a mathematical technique for
analyzing digitized waveforms and applying certain "correction
factors".  This technique was developed for the testing and
qualification of Active Board Channel Maintenance (ABCM) design used
in the ES/9000* System ABCM refers to "Hot Plugging" channel cards in
an active board, without disturbing the operation of neighboring
cards.  An overview of the test strategy is described in "Active
Board Channel Maintenance Noise Simulation and Test Method," IBM
Technical Disclosure Bulletin 35, 4A, 398-399 (September 1992, this
issue).

      Using electronic test equipment, the noise waveform can be
repeated at a rate much faster than that which can be obtained by
manually plugging the neighboring card, thus dramatically increasing
the test efficiency.

      There are two problems that arise in attempting this test
strategy.  First of all, the power plant of the card has a very low
impedance at high frequencies.  This results in loading down the
generator to the point where there is virtually no output.
Furthermore, the loading is not uniform and the out waveform is
distorted in shape. Secondly, the card has its own <'transfer
function<' and a waveform that is injected at the card pins is not
necessarily the same as what will be observed at the internal probe
point.

      The attenuation of the signal can be offset by amplification,
but here again, the amplifier gain may not be uniform and this causes
another source of distortion.

      The crux of this disclosure is a compensation scheme that is
applied to the digitized waveform before it is loaded into the
arbitrary waveform generator.  When this "adjusted" waveform is
applied to the card under test, the desired waveform is observed at
the monitoring point.  The mathematical relationship between the
original and adjusted waveforms follow the rules of linear network
theory.  Typically, a time domain input/output is related through a
convolution algorithm.  These algorithms involve many integrations
and is not practi...