Filters used in signal analysis, FIR or IIR?

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Alejandro
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Filters used in signal analysis, FIR or IIR?

Post by Alejandro »

Hi guys
I've been practicing the filtering of signals in Matlab, but, as always, I have a question..
What are the most common filters used in Geophysics? FIR or IIR? I think the FIR are more effective (and they can be designed as a linear phase Filter, and they are always stable), but at the expense of high computational cost, meanwhile the IIR are less effective than FIR (and they are not always stable), but more easy to implement. For the people that have been working with filters, which one is better, FIR or IIR? what do you recomend for geophysical applications (for example, in the seismic data analysis)?

GuyM
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Re: Filters used in signal analysis, FIR or IIR?

Post by GuyM »

Had to look those terms up:-)

I think mostly you'll see FIR filters for the reasons you describe. While these do have edge effects compared to the physical IRR filter banks, the stability - especially with phase - is highly desirable.

High computation cost doesn't mean very much these days, broadly speaking; or rather the processes that are computationally "expensive" are the ones that use large matrix transformations (ie Radon domain), sample-by-sample calculations (ie NMO), or where an output trace is the result of an multi-dimensional array of input traces (eg 3D migration or 5D interpolation)

nsm
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Re: Filters used in signal analysis, FIR or IIR?

Post by nsm »

I have used both FIR and IIR in GPR data processing, I don't see much difference.

Michael_Seman
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Re: Filters used in signal analysis, FIR or IIR?

Post by Michael_Seman »

The FIR filter would be zero-phase in seismic processing. In real-time applications, it would be delayed a little so becomes linear phase. The IIR filters would be used if you wanted a minimum phase filter, or to simulate analogue recording filter. Although in practice, the phase response is only valid up to approximately half Nyquist, because a non-linear frequency mapping is used in the computation of the filter.

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