Forums

FFT's and signal detection

Started by mickmonx June 27, 2004
Hello all,

I'm currently attempting to detect the level of the 66kHz component
of an arbitrary signal using an 56F8323, I was hoping that I could
sample the signal using the ADC (taking say 512 samples) and then
perform an FFT on these samples to give me another set of values
that relate to the frequency spectrum. I could then simply check the
value that corresponds to 66kHz.

Being new to DSP and not knowing too much about FFT's I don't know
if this is possible or if I am being over simplistic. Is an FFT the
best way of detecting the 66kHz component? Any advice, tips or
examples would be gratefully received.

Cheers

Mike



For picking off a single tone, the Goertel algorithm is a much better choice for processing efficiency. You can dig up info on the web, or in certain communications textbooks.
 
An FFT will work too, and is much easier to find code for. The # of FFT points will determine the range of frequencies that will contribute energy to the bin. i.e. more bins = narrower frequency resolution. FFT code is easy to write if you don't care about efficiency (i.e. speed of execution). There are a million people who have written FFT code, and some Motorola family/user manuals have it in the back of the book.
 
Howard
-----Original Message-----
From: mickmonx [mailto:m...@monx.co.uk]
Sent: Sunday, June 27, 2004 5:12 PM
To: m...@yahoogroups.com
Subject: [motoroladsp] FFT's and signal detection

Hello all,

I'm currently attempting to detect the level of the 66kHz component
of an arbitrary signal using an 56F8323, I was hoping that I could
sample the signal using the ADC (taking say 512 samples) and then
perform an FFT on these samples to give me another set of values
that relate to the frequency spectrum. I could then simply check the
value that corresponds to 66kHz.

Being new to DSP and not knowing too much about FFT's I don't know
if this is possible or if I am being over simplistic. Is an FFT the
best way of detecting the 66kHz component? Any advice, tips or
examples would be gratefully received.

Cheers

Mike



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Just correcting the name of the algorithm: "Goertzel algorithm"
 
Best regards,
 
Fabio Estevam
-----Original Message-----
From: Ebersman, Howard [mailto:H...@microwavedata.com]
Sent: segunda-feira, 28 de junho de 2004 10:22
To: 'mickmonx'; m...@yahoogroups.com
Subject: RE: [motoroladsp] FFT's and signal detection

For picking off a single tone, the Goertel algorithm is a much better choice for processing efficiency. You can dig up info on the web, or in certain communications textbooks.
 
An FFT will work too, and is much easier to find code for. The # of FFT points will determine the range of frequencies that will contribute energy to the bin. i.e. more bins = narrower frequency resolution. FFT code is easy to write if you don't care about efficiency (i.e. speed of execution). There are a million people who have written FFT code, and some Motorola family/user manuals have it in the back of the book.
 
Howard
-----Original Message-----
From: mickmonx [mailto:m...@monx.co.uk]
Sent: Sunday, June 27, 2004 5:12 PM
To: m...@yahoogroups.com
Subject: [motoroladsp] FFT's and signal detection

Hello all,

I'm currently attempting to detect the level of the 66kHz component
of an arbitrary signal using an 56F8323, I was hoping that I could
sample the signal using the ADC (taking say 512 samples) and then
perform an FFT on these samples to give me another set of values
that relate to the frequency spectrum. I could then simply check the
value that corresponds to 66kHz.

Being new to DSP and not knowing too much about FFT's I don't know
if this is possible or if I am being over simplistic. Is an FFT the
best way of detecting the 66kHz component? Any advice, tips or
examples would be gratefully received.

Cheers

Mike



_____________________________________
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_____________________________________
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