[time-nuts] External clock for Analog to Digital Converter in GPS Rx front-end

Hal Murray hmurray at megapathdsl.net
Fri Mar 2 02:27:16 EST 2007

> I am working on Jitter in Analog to Digital Converters(ADCs) for GPS
> receiver front-end. I am trying to setup an experiment to see the
> effects of jitter in real time ADCs. I have an ADC evaluation 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.  

Add noise, perhaps by attenuating the signal a whole lot and then amplifying 
it back up the the desired level.  But you won't know what sort of jitter you 
get that way.

Lots of signal generators have a modulation option.  If you feed a signal in 
there, that gives you a signal other than a pure sine wave.  It's predictable 
rather than noise so that may not be what you want.  Of course, you could 
feed noise into the external modulation input.  Rock music might be good 
enough.  Or speech.  Whatever is on the radio or TV or your CD player.

These are my opinions, not necessarily my employer's.  I hate spam.

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