External clock for Analog to Digital Converter

Feb 27, 2007 1 Replies
B

Hi Everyone, I am working on Jitter in Analog to Digital Converters(ADCs). I am trying to setup an experiment to see the effects of jitter in real time ADCs. I have an ADC evalutaion board with external clock input for sampling (i.e Sampling clock). Now I want to produce a self created jittery signal to see the effects of jitter in ADC. Can anyone out there have any idea(s) how I can produce a real time clock signal with "variable jitter" for the input of external clock? Producing a simple clock signal (i.e. without jitter) is straight forward with the help of any signal generator but a clock signal with "variable jitter" is a problem.



Thanks for your help.



Cheers



Bilal



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B

This may be a whole lot easier than you think, depending on how much jitter you need. If you simply add the good clock signal and some other modulating signal through a simple resistive mixer into the input of a logic gate, the modulating signal will bias the clock to hit the gate threshold earlier or later than otherwise. Works best if the clock has slow edges, which you might want to encourage by a bit of capacitance at the gate input.

If you want a modulating source with plenty of options (uniform white, pink, gaussian, band-limited noise, standard waves, arbitrary waveforms, AM, FM, bursts, sweeps, etc) you can use the sound card signal generator in my Daqarta package. (Daqarta is shareware, but the signal generator keeps working after the trial period so that part is effectively freeware.)

Best regards,

Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis

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Scope, Spectrum, Spectrogram, Signal Generator Science with your sound card!

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