# Questions tagged [magnitude]

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### Why are magnitudes normalised during synthesis (IDFT), not analysis (DFT)?

In most examples and FFT code that I've seen, the output (frequency magnitudes) of the forward DFT operation is scaled by N -- i.e. instead of giving you the magnitude of each frequency bin, it gives ...
44k views

### Power spectral density vs. FFT bin magnitude

What's the difference between these? Both are measurements of some form of signal power, but surely there's some difference between the power they are measuring?
5k views

### How does zero-padding affect the magnitude of the DFT?

Let's simulate sinusoids of two frequencies using the following Matlab code: ...
11k views

### Identifying the magnitude and impulse response from pole zero plot quickly

I have an exam next week and it's verty certain that a task of this kind will be there. Are there some good tips how to match the right pole zero plot to the right responses? No proof is needed in ...
20k views

### Energy calculation in frequency domain

I was just wondering... The formula I learned to calculate the energy of the signal is expressed in the time domain: $E_x^{\text{time}} = \sum_{n=-\infty}^{\infty} |x[n]|^2$ Then, what does the ...
4k views

### Adequate representation of frequency domain amplitude/magnitude of FFT of a signal

I'm quite new to the subject and am having fun playing around with the FFT. What I am currently doing is trying to sample an audio signal and display its frequency spectrum at the same time. This ...
3k views

### recover image by only magnitude of image fourier transform

I have a image and I want calculate fft2 of it, after it I want recover image only by magnitude of it. how can I achieve this work? ...
80 views

874 views

### Magnitude response and DFT normalization

Suppose I have an FIR denoted h that represents the impulse response of a system. Using MATLAB syntax (for convenience and brevity), What does ...
681 views

### How to reconstruct signal of its phase and magnitude functions?

I have two continuous periodic (a period of $2\pi$) functions which belong to the phase and magnitude of Fourier transform of a signal, how can I reconstruct the original signal? What kind of ...
5k views

57 views

### Computing real signal with minimum absolute values from even magnitude spectrum

I want to derive a real audio signal from an arbitrary even magnitude spectrum. The phase spectrum affects the values of the signal in the time domain; for example, a phase of 0 for all frequencies ...
76 views

### zero-phasing frequency components while keeping the same magnitude, in Matlab

How is it possible? I was thinking of taking just the real part of the DFT of my signal (isn't that zeroing out phases?) with real(fft(X)) but the magnitudes ...
752 views

### sketching magnitude of frequency response of H(z)

I am trying to plot the magnitude of H(z), I got it to factore, and would like to sketch its plot of magnitude. But I am have trouble evaluating the function.  H(z)= \frac{(1-2z^{-1})(1+0.5z^{-1})(...
257 views

### Interpreting magnitude of DFT results

I'm working on creating a simple program to render spectrograms like this one. In this plot, the X-axis is time, the Y-axis is frequency, and the color represents the magnitude of the DFT at that ...
1k views

### Magnitude Spectrum, different magnitudes same amplitude

When the following code is written,the resulting magnitude spectrum shows magnitude values represented by two peaks is different even though they have the same amplitude. why is that? a fast reply ...
844 views

### Matching an LPC Magnitude Spectrum to FFT Magnitude Spectrum

I'm trying to get an LPC magnitude spectrum to match to an FFT magnitude spectrum. Basically I want the peak height in the LPC Spectrum to match the peak height in the FFT Spectrum. Thanks to ...
32 views

### FFT frequency-magnitude not correct when a positive gain EQ point is applied

I have a measurement system, which applies a log sine sweep as stimulus to a DUT and records the return signal. I then extract the impulse response, and perform an FFT on this to examing phase and ...
53 views

### Correctly scaling FFT of different lengths

I have been looking at using two FFTs of different lengths and displaying the output magnitudes on the same graph (a shorter length window for the higher frequencies, and a longer one for lower ...