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Topic: Difference in cumsum/filter
Replies: 1   Last Post: Feb 23, 2013 12:38 AM

 Messages: [ Previous | Next ]
 Peter Mairhofer Posts: 41 Registered: 8/18/10
Difference in cumsum/filter
Posted: Feb 22, 2013 11:42 PM

Hi,

I want to create an ideal, analog integrator for function x(t). Given
that x(t) is BL to 500Hz, the integration of a signal x=randn(1000,1)
can be replaced by a cumulative sum:

y1 = cumsum(x)

On the other hand, I can transfer the ideal integrator 1/s to z-domain
and filter the signal with that:

[numd, dend] = bilinear([1], [1 0], 1000);
y2 = filter(numd, dend, x) * 1000;

This works but the error is quite large; I would expect numerical
precision under these ideal conditions:

http://snag.gy/jsThi.jpg

What is wrong here and can I fix this?
Thanks,
Peter

Date Subject Author
2/22/13 Peter Mairhofer
2/23/13 Peter Mairhofer