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digital_filter [message #58327]

Mon, 28 January 2008 06:46

claire.maraldi
Messages: 4
Registered: January 2006

Junior Member

Hi,

I have a problem of comprehension with the digital filter tool.

I have an array "X" of n elements, the delta between two elements is
"1unit"
I would like to creat a pass band filter between 1unit and 60 units

In IDL I write

; Filtre : 1unit<T<60unit ;
delta=1. ;
f_low=1./(60.*1.)
f_high=1./(1.*1.)
a_ripple=50. & nterms=40.
coeff=DIGITAL_FILTER(f_low*2*delta, f_high*2*delta, a_ripple, nterms)

X_filter=convol(REFORM(X),coeff,/EDGE_TRUNCATE)

Then when I compute FFT(X_filter), I see than my signal has been cut
between 1 unit and more than 60units (about 100 units). Are my
definitions of f_low and f_high wrong, or is this a problem related to
the digital_filter function ?

Thanks
Claire

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[Message index]

		digital_filter By: claire.maraldi on Mon, 28 January 2008 06:46
		Re: digital_filter By: Wox on Tue, 29 January 2008 05:13

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