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Trigger-Jitter Correction in Noise Measurements

IP.com Disclosure Number: IPCOM000099187D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-14
Document File: 2 page(s) / 58K

IBM

Related People

Mukherjee, A: AUTHOR [+2]

Abstract

This article describes a method for performing measurements in the playback of magnetic signals. The method steps include (a) generating trigger from the playback signal by delaying it by a time and comparing it with the original (b) waveform recording at a fixed time t after the point, (c) measuring the digitized waveform as a of time on playback, (d) measuring the variation in of the trigger point, and (e) generating the spectrum of signal-dependent noise. for Trigger Jitter

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Trigger-Jitter Correction in Noise Measurements

measurements in the playback of magnetic signals.  The method steps
include (a) generating trigger from the playback signal by delaying
it by a time and comparing it with the original (b) waveform
recording at a fixed time t after the point, (c) measuring the
digitized waveform as a of time on playback, (d) measuring the
variation in of the trigger point, and (e) generating the spectrum of
signal-dependent noise. for Trigger Jitter

Let S(t) and N(t) be the signal and noise respectively, are
being measured.  Assume that the average value of is zero for all t.
In the presence of trigger jitter, measured waveform R(t) is given by
= S(t + w) + N(t + w)  w is a random variable representing the
trigger  It can be shown that under certain reasonable  Z E(R(t)) -
var(w).(E(R"(t)))   Z var (R(t)) - var(w)(E(R'(t)))2  E(.) means
expectation (averaging) and var(.) means

Equation (3) shows that by measuring the read-back R(t), and
the variance of the trigger jitter, one get the variance of the noise
N(t).  The trigger jitter obtained by measuring the time difference
between two pulses, separated by a time  T.  An important for
Equations (2) and (3) is that w is of N(t).  In practice, the
correlation between w N(t) is made small by choosing T long enough,
as previously.  T, however, cannot be so long that speed variations
become important.  The f...