ssahuiit@rediffmail.com wrote in message news:<2ce2ab3c.0307040100.4b2dddc2@posting.google.com>...
> I have a query on zero-padded FFT's.For calculating FFT of a signal
> with sampling rate 256 HZ what is the maximum zero padding that can
> be done?
Zero padding appends artificial data points of value 0 to the
finite data series. The amount of artificial data points that
can be appended would probably be limited by system memory.
> And what does zeropadding actually do to the signal.
It interpolates the spectrum.
> I have
> observed frequency shift with zero padding.why so?
The values of the DFT coefficient are constrained on the spectrum
lines that also are found in the DFT of the non-zero padded sequence.
However, the gradient is not, so one might see situations where
the interpolated spectrum has a positive gradient dX/df on one "true"
line and a negative gradient on the nex, which means there would be a
maximum in between. It's can be regarded as an artifact of the
interpolation.
Rune
Reply by Dominiek●July 4, 20032003-07-04
Zero padding actually more or less interpolates the frequency domain
points you would have without zero padding. Frequency shifts are
impossible in this respect.
I don't really know what you mean by 'maximum zero padding'...
Ciao,
Dominiek
ssahuiit@rediffmail.com wrote in message news:<2ce2ab3c.0307040100.4b2dddc2@posting.google.com>...
> I have a query on zero-padded FFT's.For calculating FFT of a signal
> with sampling rate 256 HZ what is the maximum zero padding that can
> be done?And what does zeropadding actually do to the signal. I have
> observed frequency shift with zero padding.why so?
Reply by ●July 4, 20032003-07-04
I have a query on zero-padded FFT's.For calculating FFT of a signal
with sampling rate 256 HZ what is the maximum zero padding that can
be done?And what does zeropadding actually do to the signal. I have
observed frequency shift with zero padding.why so?