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Modeling >> Behavioral Models >> ADC two step converter
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Message started by solanojedi on Aug 4^th, 2010, 9:15am

Title: ADC two step converter
Post by solanojedi on Aug 4^th, 2010, 9:15am

Hi everybody,
I have to design a model for an ADC two step converter using a block that behaves like the non-linear function of the residue (as on page 5 of http://www.eecs.umich.edu/~mpflynn/teaching/design_contest/winter_2004/presentations/RalphLi.pdf ) in Simulink.

I'm a newbie of Simulink, so I figured to use the block "MATLAB fcn" to define the saw toothed function: in a matlab file .m I can describe the behaviour of the block. For example, if u is the input and out is the output, if I write out=cos(u) at the output I will see the cosine of the input u.
So I simply tried this: I use a ramp, a MATLAB fcn with the function out=cos(u) and then I look at the output with a scope, but what I see is the picture attached. Maybe it's a stupid question but....why? :( I should see a cosine...
Thank you very much!

Nicola

Title: Re: ADC two step converter
Post by Marq Kole on Feb 2^nd, 2011, 6:09am

As far as I can see your sampling of the output signal is too coarse. You need to set a maximum time step in the simulation setup of Simulink that is a factor of ~5 or more larger than the period of your cosine signal.

Cheers,
Marq