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From: djt294 on 2 Mar 2010 14:23
Hi,
I want to compute an fft using a microcontroller with a hardware
multiplier. I saw an application note from maxim which stated that the
fft inputs and outputs are in Q format. If I get the samples from my
ADC in 2's complement format do I need to convert that into Q format
to do the computations?


thanks,
djt294
From: Tim Wescott on 2 Mar 2010 14:39
djt294 wrote:
> Hi,
> I want to compute an fft using a microcontroller with a hardware
> multiplier. I saw an application note from maxim which stated that the
> fft inputs and outputs are in Q format. If I get the samples from my
> ADC in 2's complement format do I need to convert that into Q format
> to do the computations?

Usually 'Q' format is a bit-shifted two's complement, but it's not like
there are any ISO standards are anything -- so it's kind of up to you to
dig out what Maxim means.

If their 'Q' format _is_ bit-shifted two's complement, then you can just
use their FFT routines.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
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