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Re: Using IDL to make a signal filter [message #61365 is a reply to message #61280]

Mon, 14 July 2008 08:06

Kenneth P. Bowman
Messages: 585
Registered: May 2000

Senior Member

In article
<6961630e-ccbc-4e50-82c4-9124498ec7a0@s50g2000hsb.googlegroups.com>,
ICBM0926 <ICBM0926@gmail.com> wrote:

> I have an 1D vector data in IDL from an analytical laser formula which
> contains 2 laser frequencies. I wrote a program trying to filter my 1D
> vector and get the waveform of one of the frequencies. I used 1D FFT
> and a mask
> function(step function). I applied the mask function to the frequency
> domain data. I've covered both positive and negative frequencies. I
> did inverse 1d FFT to retrieve the signal. I found that
> the amplitude of the signal is only half as it should be. Could
> anybody tell me what went wrong?

It sounds like you are doing things right, but it is easy to
make mistakes using FFTs.

You might want to look at the chapter on FFTs in my book
(http://tinyurl.com/zavp9), or create an artificial input
data set where you know exactly what the answer is and
use that to test your software.

Ken Bowman

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[Message index]

		Using IDL to make a signal filter By: ICBM0926 on Mon, 14 July 2008 04:08
		Re: Using IDL to make a signal filter By: Wox on Tue, 15 July 2008 02:32
		Re: Using IDL to make a signal filter By: Wox on Mon, 14 July 2008 10:33
		Re: Using IDL to make a signal filter By: Kenneth P. Bowman on Mon, 14 July 2008 08:06

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