Proper Scaling of FFT of an non-periodic signal
I am trying to calculate the FFT of some sampled data, and have had
some trouble determining the correct way to scale the resulting FFT
Technical note 1703 states to properly scale the FFT (Mx) of a signal
(x), the FFT should be divided by N, where
However, I have determined that this only applies for the case where
the signal x is <periodic>.
What I want to know is how to scale the FFT is the signal is NOT
periodic. Is there a way to accomplish this? I need to determine the
proper magnitude of the FFT for data resulting from an input
sine-sweep, or from a series of...FFT of a known periodic signal of arbitrary length with a radix-2 algorithm
I've browsed a bit, so hopefully I've got all my information in order.
I haven't been able to find an answer for this specific problem.
It's for image processing. I'm simplifying 2D regions by applying
low-pass filters to their contours. Specifically, I take an 8-connected
clockwise contour of (arbitrary) n points, and make two new functions,
x(i) and y(i), out of the points' coordinates. Then I do a DFT on each,
apply a Gaussian or low-pass cutoff filter, inverse DFT, and replot. It
works like a charm if I use a naive O(n^2) DFT implementation - but of
course, it'...FFT scaling of array/FFT scaling of differential function
I have a problem with scaling my graphs for FFT functions.
I am currently implementing forced oscillators and the result output is from the following code
[t x] =ode45(@vanderpol, 0:2*pi/100:4000, [0 1]);
This returns the correct output array. When i transform this however the graphs are not scaled- can someone please help?
i used the following code to transform:
I have looked at alot of different forum posts and can't get help with this (i have tried multiple methods) ... can anyone help me?
Thanks in advance.
...About FFT (Periodic, non-periodic)
I have read 'a guide to the FFT' in the 'File exchange'
, but confusing about the FFT
The author recommend the following commands
when we'd like to see the spectrum in the frequency domain.
1. fftshift(fft(fftshift(�)))/Fs for (non-periodic signal)
Here, Fs: sampling frequency
2. fftshift(fft(fftshift(�)))/Np for (periodic signal)
Here, Np:number of samples
But what's the difference? and Should i have to divide it
by Np for periodic signal?
beom lee wrote:
> I have read 'a guide to the FFT' in the 'File exchange'
> , but co...FFT Scaling to 0dB (full-scale)
I have a basic question about the fft() function. Let's say I create
a whitenoise signal that has peaks from +1 to -1. When I run a fft
on this signal it shows me amplitudes in the positive dB! I thought
that a full-scale signal should only have frequency peaks up to 0dB.
Currently, I have peaks upwards of 25dB.
Even when I scale the signal down to +0.6 and -0.6, I still see data
higher than 0dB. Is there a way in Matlab to somehow tell the fft
function what full-scale is equal to?
Here is the code I have so far for a test...
...convolution between periodic signal and random signal
I am trying to convolve a sine wave with a random signal.
Instead of using conv function, I am multiplying them in the
frequency domain and then taking the ifft. I have taken care
of the zero padding issue in the time domain. The problem is
instead of getting a dual-dirac histogram, I always end up
with the histogram of random signal. Can anyone suggest a
proper convolution code between a sine wave (or any periodic
waveform) and random signal?
Thanking everyone in advance.....
Check the fft of the sine wave alone - do you get two peaks and zeros
everywhere else? (To get this...Divide periodic signal into periodic and nonperiodic components
I would like to know is it possible to divide a periodic signal into 2 composite signals: one periodic and the other non-periodic?
If possible, can anyone please give me a hint on how to do so ?
On 9 Feb, 14:01, "gehan Mustafa" <g...@gigi.com> wrote:
> Dear all,
> I would like to know is it possible to divide a periodic signal into 2 composite signals: one periodic and the other non-periodic?
Periodic components are prefectly predictable.
Try to use some sort of linear prdiction.
Rune Allnor <firstname.lastname@example.org> wrote in message <5b5e4...Analyzing input signal and periodic signal generation
I need to do data acquisition of a voltage (sine wave) and at a
specific angle of the ideal sine wave after a fixed number of periods
have been acquired an analog signal has to be sent. Knowing the input
signal's frequency, phase information I can guess the time to wait
before the same point on the wave comes. I use 'get time.vi' and
wait until the predicted time comes' using a while loop that checks
if the real time is equal to the predicted time. Problem is program
misses the target point. I mean if my predicted time is 1.324 ms
although the program counts milliseconds it...fft from a signal
My purpose is to transform my time series B to the frequency domain.
and then with a notch filter remove the specific frequency of 1/24[hour]
I figured out this fft code for my data but I am not sure that the frequency is in Hertz or not?
And I do not know how notch filter works?
I recently started Matlab signal processing. I really appriciate if help me with this.
%Time Sampling Interval=1[hour]=3600[second] =>FS=sampling frequency =[1/3600]HZ
%time vector in second= (0:N-1)/FS
%time vector in hour= t = ((0:N-1)/FS)/3600
%%signal in frequency domain