Author Topic: RD JDS6600 Signal Generator - jitter on pulse output when duty cycle is not 50%  (Read 2005 times)

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Offline ArcticGeek

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I recently purchased the RD JDS6600 40MHz signal generator from a US vendor on ebay, and received it last week.  For the most part I was pleased with the unit, until I discovered this anomaly.  When you generate a pulse output with a duty cycle other than 50%, you end up with 5ns of jitter on the pulse. 

I am including some scope shots that show this behavior.  I have the generator configured to generate a 1VPP pulse, it is connected to my scope (with 50 \$\Omega\$ termination enabled) using a RG-58 cable. 

The first image is a 10MHz pulse with 50% duty cycle, this looks fine.  The second image is the same frequency but a 40% duty cycle, you can see the 5ns jitter.  The next 2 images are taken at 20% duty cycle at 10MHz.

I then tried a few other frequencies, I've included a picture of  a 1MHz 40% duty cycle and 500KHz at 60% duty cycle....the 5ns jitter remains.  It really doesn't matter what frequency, anything with a duty cycle other than 50% has this problem.  To make sure I wasn't having some sort of triggering problem with my scope, I dug out my boat anchor HP 8116A function generator, and a 10MHz 40% pulse looks as it should (show in the last picture).  So this is odd behavior unique to the JDS6600 unit.

I am assuming that the 5ns jitter comes from the 200MHz sample rate that the unit has.  I don't really know how DDS signal generators work, but I am assuming this 5ns is an artifact of the 200MHz base clock.   Is my assumption correct?

To investigate a bit futher a took a look at a 10MHz 40% duty cycle pulse on a HP33120A generator, and it looks fine with no jitter.

So what's up with this?   Has anyone else observed this?   Does a Feeltech FY6600 have this same issue?   If not I might send this thing back.
 


Offline ArcticGeek

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@pantelei4:

Thanks for the link.  I actually did a search before I posted and ran across that thread, but I never saw the discussion about the jitter - I skimmed right over it.  Thanks!

Does anyone know if the FY6600 Feeltech has this same issue?   I really don't like it for a lot of the stuff I am doing.

 


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