Alternative to fourier transform

R

Rene Tschaggelar

Guest
There was this alternative to the FFT being mentioned a
few months ago. It was to be continous in time and not
blockwise.
As I remember, it was said to be advantageous in cases
where 499.9Hz and 500Hz are to be resolved.
I lost the reference to it, a name would be sufficient.

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net
 
Rene Tschaggelar wrote:

There was this alternative to the FFT being mentioned a
few months ago. It was to be continous in time and not
blockwise.
As I remember, it was said to be advantageous in cases
where 499.9Hz and 500Hz are to be resolved.
I lost the reference to it, a name would be sufficient.

Rene
Click to expand...
If you're only trying to distinguish between those two frequencies then
a plain old IIR bandpass filter would probably be appropriate.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
 
On Thu, 30 Dec 2004 00:29:38 +0100, Rene Tschaggelar wrote:

There was this alternative to the FFT being mentioned a
few months ago. It was to be continous in time and not
blockwise.
As I remember, it was said to be advantageous in cases
where 499.9Hz and 500Hz are to be resolved.
I lost the reference to it, a name would be sufficient.
Click to expand...
Wavelet?

--
Best Regards,
Mike
 
On Thu, 30 Dec 2004 00:29:38 +0100, Rene Tschaggelar <none@none.net>
wrote:

There was this alternative to the FFT being mentioned a
few months ago. It was to be continous in time and not
blockwise.
As I remember, it was said to be advantageous in cases
where 499.9Hz and 500Hz are to be resolved.
I lost the reference to it, a name would be sufficient.
Click to expand...
The Goertzel algorithm perhaps?

http://www.embedded.com/story/OEG20020819S0057

--
Rich Webb Norfolk, VA
 
It depends on what you're doing.

If the signal has no noise and well-defined zero crossings, just
measuring the period will tell you whether you've got 499.9Hz or 500Hz
in a single cycle. (Or half-cycle if you guarantee a square wave).

If other frequencies are present and/or noise etc., but you still have
to measure the amplitudes at a small number of frequencies (your
example named two, other applications like DTMF might have 8), then IIR
bandpass filters work nicely and you don't have to do Fourier at all.

Fourier is nice and all that if you really need to know amplitude and
phase for each and every bin, but most applications simply don't need
anything like that and are easily satisfied with a miniscule amount of
computational horsepower.

Tim.
 
Rene Tschaggelar wrote:
There was this alternative to the FFT being mentioned a
few months ago. It was to be continous in time and not
blockwise.
As I remember, it was said to be advantageous in cases
where 499.9Hz and 500Hz are to be resolved.
I lost the reference to it, a name would be sufficient.
Click to expand...
The Maximum Entropy method? Lomb periodogram? (Just
wild guesses).

http://www.library.cornell.edu/nr/cbookcpdf.html

Regards,
Mikko
 
Yes, the Goertzel algoorthim. Can be used for DTMF decoding, if thats what the OP had in mind. An issue of Embedded Systems had a
great article on it.

Cheers

"Rich Webb" <bbew.ar@mapson.nozirev.ten> wrote in message news:kil6t0p7lf0umoaoagsq9hlsqbefeqb9ph@4ax.com...
On Thu, 30 Dec 2004 00:29:38 +0100, Rene Tschaggelar <none@none.net
wrote:

There was this alternative to the FFT being mentioned a
few months ago. It was to be continous in time and not
blockwise.
As I remember, it was said to be advantageous in cases
where 499.9Hz and 500Hz are to be resolved.
I lost the reference to it, a name would be sufficient.

The Goertzel algorithm perhaps?

http://www.embedded.com/story/OEG20020819S0057

--
Rich Webb Norfolk, VA
Click to expand...
 
Rene Tschaggelar wrote:
There was this alternative to the FFT being mentioned a
few months ago. It was to be continous in time and not
blockwise.
As I remember, it was said to be advantageous in cases
where 499.9Hz and 500Hz are to be resolved.
I lost the reference to it, a name would be sufficient.

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net
Click to expand...
wavelets.
http://www.tinaja.com/wave01.asp

--
Many thanks,

Don Lancaster
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
voice: (928)428-4073 email: don@tinaja.com

Please visit my GURU's LAIR web site at http://www.tinaja.com
 
The chirp-z transform can resolve between arbitrary frequency points.
This function is available in Matlab, otherwise code to do is posted on
the net.

Tom
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top