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Re: Difference in cumsum/filter
Posted:
Feb 23, 2013 12:38 AM


On 20130222 20:42, Peter Mairhofer wrote: > Hi,
Sorry, found the problem for myself.
> 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)
This assumes that x(t) is /not/ a piecewise constant function but rather a sinc interpolation (x(t) is BL to 500).
Therefore it is not an exact result but rather an approximation with the finite Riemann sum
> On the other hand, I can transfer the ideal integrator 1/s to zdomain > and filter the signal with that: > > [numd, dend] = bilinear([1], [1 0], 1000); > y2 = filter(numd, dend, x) * 1000;
And this does the "real" integration based on the same assumptions on x(t).
Peter



