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From: Fred Marshall on 28 Jul 2010 13:48
bharat pathak wrote:
> Hello All,
>
> Lets say,
>
> N = 32;
> n = 0 : N-1;
> fin = 1500 hz;
> Fs = 48000 hz; % Fs/fin = 32/1
>
> xn = sin(2*pi*fin*n/Fs + theta)
> xk = fft(xn)
>
> If Fs and fin are exact mutiple, if i have theta non-zero,
> will it cause spectral leakage in FFT mag response, or it will
> show up as an added offset in the phase plot?
>
> Regards
> Bharat

I'd like to think that there are no dumb questions. So, I will answer
in some fashion:

- Each sample in the FFT has Real and Imaginary parts or Magnitude and
Phase. Right? You know this, right?
So, if the phase is changed in any sample, then what happens to the
magnitude?
Hint: "Nothing" is the right answer.

- There is no "phase plot" in the expressions given. Are we supposed to
assume what you mean exactly?
Hint: If you change the phase, it will change the phase.

Fred
From: HardySpicer on 28 Jul 2010 15:30
On Jul 29, 1:58 am, "bharat pathak" <bharat(a)n_o_s_p_a_m.arithos.com>
wrote:
> Hello All,
>
>     Lets say,
>
>     N   = 32;
>     n   = 0 : N-1;
>     fin = 1500 hz;
>     Fs  = 48000 hz; % Fs/fin = 32/1
>
>     xn  = sin(2*pi*fin*n/Fs + theta)
>     xk  = fft(xn)
>
>     If Fs and fin are exact mutiple, if i have theta non-zero,
>     will it cause spectral leakage in FFT mag response, or it will
>     show up as an added offset in the phase plot?
>
> Regards
> Bharat

Phase is a relative measure to have any meaning at all, so you would
need something to measure phase with respect to.
No it doesn't!

Hardy
From: bharat pathak on 28 Jul 2010 23:13
I was just trying to understand FFT and the presence of sine and
cosine terms present as the basis functions. I dont know whats wrong
in asking questions and why cant experts make mistakes in understanding.

Long time back I had pointed an "understanding error" in Rick Lyons book.
and he acknowledged the same. While discussion I had figured it out that
his assumptions were wrong to begin with. Does that mean he does not
know DSP?

Regards
Bharat




From: Vladimir Vassilevsky on 28 Jul 2010 23:39


bharat pathak wrote:
> I was just trying to understand FFT and the presence of sine and
> cosine terms present as the basis functions.

Hm. What it should mean?

> I dont know whats wrong
> in asking questions and why cant experts make mistakes in understanding.

Oh, nothing wrong. You may even become a PhD.

> Long time back I had pointed an "understanding error" in Rick Lyons book.
> and he acknowledged the same. While discussion I had figured it out that
> his assumptions were wrong to begin with. Does that mean he does not
> know DSP?

"Stupid is as stupid does", as Forrest Gump used to say.

> Regards
> Bharat

VLV
From: robert bristow-johnson on 29 Jul 2010 00:50
On Jul 28, 11:39 pm, Vladimir Vassilevsky <nos...(a)nowhere.com> wrote:
> bharat pathak wrote:
> > I was just trying to understand FFT and the presence of sine and
> > cosine terms present as the basis functions.
>
> Hm. What it should mean?
>
> > I dont know whats wrong
> > in asking questions and why cant experts make mistakes in understanding..
>
> Oh, nothing wrong. You may even become a PhD.
>
> > Long time back I had pointed an "understanding error" in Rick Lyons book.
> > and he acknowledged the same. While discussion I had figured it out that
> > his assumptions were wrong to begin with. Does that mean he does not
> > know DSP?
>
> "Stupid is as stupid does", as Forrest Gump used to say.
>
> > Regards
> > Bharat
>
> VLV

i think it's Simon Cowell spoofing Vlad V. i didn't make it to the
comp.dsp conference to meet "Vladimir" (who i am sure is Simon Cowell)
first hand, so i leave it to those who did to verify my suspicion.

r b-j
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