RE: [SI-LIST] : Jitter measurement

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From: Thomas Jackson (tjackson@fmi.fujitsu.com)
Date: Mon Mar 19 2001 - 10:39:23 PST


Let me be a contrarian.

I think the best way to measure oscillator jitter is with a good counter,
ideally a time interval measurement system. The accuracy of most counters
is much, much better than the timebase in oscilloscopes, real-time or
sampling. Make multiple measurements of the period and calculate some
statistics: max, min, mean, sigma, etc.

If you do use an oscilloscope, over the long-term, both should provide
equivalent results, assuming they both have the same timebase accuracy and
stability. If I understand sampling oscilloscopes correctly, they make one
(1) sample per trigger and build up a trace from a number of widely spaced
samples. Real-time oscilloscopes take a number of consecutive samples when
triggered. If the oscillator has a lot of jitter, it seems to me that a
real-time measurement will converge on the measurement faster.

Tom

Thomas L. Jackson, P.E.
Staff VLSI Design Engineer
Network Access Development
Systems Solutions Group
FUJITSU MICROELECTRONICS, INC.
3545 North First Street
San Jose, CA  95134-1804
telephone: (408) 922-9574
facsimile: (408) 922-9618
http://www.fujitsumicro.com

-----Original Message-----
From: Sunil Kumar [mailto:sunilb@cdotb.ernet.in]
Sent: Monday, March 19, 2001 7:05 AM
To: si-list
Subject: [SI-LIST] : Jitter measurement

Hello everybody..

I want to measure cycle-to-cycle jitter generated by a crystal
oscillator. I have two options:
        
        1) Real time oscilloscope
        2) Sampling oscilloscope

The bandwidth of the real time oscilloscope is enough for my
measurements. Both the oscilloscopes are equipped with jitter
measurement packages. Can anybody suggest which method is better?
And why?

Thanks a lot..

Sunil Kumar

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