Date: Nov 17, 2012 6:10 AM
Author: Nasser Abbasi
Subject: Re: question on fft example
On 11/17/2012 4:49 AM, Greg Heath wrote:
> "Nasser M. Abbasi" <email@example.com> wrote in message <firstname.lastname@example.org>...
>> On 11/15/2012 2:33 AM, oversky wrote:
>>> The mathwork fft example in the following link,
>>> why do we double abs(Y(1:NFFT/2+1) when plotting the amplitude?
>> This was talked about before. can google it. Here is my take on it:
>> "Why does it multiply by 2?"
> To represent the same average power as the doublesided frequency representation.
> the DC and Nyquist components should NOT be doubled.
> plot((0:Fs/2), [abs(Y(1)), 2*abs(Y(2:NFFT/2)), abs(Y(NFFT/2+1)) ] )
> Hope this helps.
Its been a while since I looked at this myself, so I am rusty now
to remember all the details (that is why I write down everything
before I forget it) but there were different views on these scaling
factors. Here is the same question, asked in 2009 here FYI