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Help for FFT point on C6713 platform

Started by suman_urfeeling August 28, 2009
Dear All

I am using c6713 dsk with CCS software. it's sampling frequency minimum 8KHz , max 99KHz & 256 FFT point. I want to process real signal 0.5Hz to 10 Hz. Is it possible to process or do FFT for this frequency band ? If not, how can i do it ...

Your kind help will be highly appreciated.

Regards

Gopal Sarkar, Kolkata

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Gopal-

> I am using c6713 dsk with CCS software. it's sampling frequency
> minimum 8KHz , max 99KHz & 256 FFT point. I want to
> process real signal 0.5Hz to 10 Hz. Is it possible to process or
> do FFT for this frequency band ? If not, how can i do
> it ...

At 100 kHz Fs, 256-pt FFT with no overlap, you would need to do an FFT every 2.56 msec. That's no problem for a 300
MHz 6713. However, as you add more processing and algorithms, you would want to carefully measure the time required
by each of your signal processing blocks, and make sure overall that your code stays within real-time.

Also I might point out that 256 pt FFT with Fs = 8 kHz is about 31 Hz per bin, and with Fs = 100 kHz is about 390 Hz
per bin. So you will not be able to "see" (resolve) a 10 Hz signal unless you either a) increase FFT size or b)
reduce Fs, for example apply an FIR decimation filter in your code prior to the FFT. Either way will require more
real-time processing.

-Jeff

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