Questions tagged [magnitude]
The magnitude tag has no usage guidance.
0
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2answers
84 views
How to graph magnitude plots for basic 4-pole filters?
I have developed magnitude plots for basic one-pole and two-pole filters derived from various Physics PDF's and tutorials I have found online and calculated from:
https://www.desmos.com/calculator/...
1
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3answers
96 views
$e^{j\omega}$ on unit circle
I am new to DSP, and I'm self studying. I am confused about the magnitude of $e^{j\omega}$ - where $\omega$ is the normalized angular frequency - when we are on the unit circle.
According to the ...
2
votes
1answer
42 views
Given a plot of both the magnitude $|H(\omega)|$ and its angle, How can you find the $H(\omega)$?
I'm specifically trying to use an inverse Fourier Transform to find $h(t)$, but I'm finding it difficult to get $H(\omega)$ in the first place.
I'm under the impression from my textbook that $H(\...
1
vote
1answer
151 views
Spectrogram with square or non-square magnitude of STFT: power vs. magnitude
As seen in this question and answer, to do a spectrogram, it's common to plot either:
the square magnitude $|\text{STFT}(\text{frame}, \text{bin})|^2$ ("power spectrum")
the magnitude $|\text{STFT}(\...
1
vote
3answers
308 views
How do I calculate peak amplitude of the signal components after zero padding and FFT?
I am learning about DFT and trying to apply it to some audio processing. I am new to DSP but experienced in programming and have some background in math and physics. The FFT algorithm I use (lomontFFT)...
0
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0answers
14 views
Do the magnitude of the signal changes in the wavelet filtering
I am using Daubechies 4 wavelets to extract a required signal.
In my signal there is a magnitude change. My raw signal lies from $-3$ to $3$, but when I choose the detail coefficients of the Db4 ...
0
votes
1answer
98 views
Summing magnitudes of individual frequency bins
I am working on signal analyser and have problem with understanding relationship between display resolution and frequency resolution (range).
My frequency range is $ 1-20000\quad [ H z ] $ so to ...
3
votes
1answer
83 views
Why harmonic components appear only after a certain level when a signal is clipped?
I recently observed this phenomenon that when a signal is clipped the harmonics start to appear only after a certain level.
The Python code to reproduce the effect is given below. The signal has 3 ...
0
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2answers
111 views
Phase information from product of complex conjugate transfer functions
For an input signal $x(t)$ and output signal $y(t)$ through an LTI system I $H(t)$ I have found and interesting property that concerns signals' power spectral densities:
$${\lvert H(\omega)\rvert}^2 =...
0
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1answer
50 views
Computing real signal with minimum absolute values from even magnitude spectrum
I want to derive a real audio signal from an arbitrary even magnitude spectrum.
The phase spectrum affects the values of the signal in the time domain; for example, a phase of 0 for all frequencies ...
1
vote
1answer
480 views
Magnitude response and DFT normalization
Suppose I have an FIR denoted h that represents the impulse response of a system. Using MATLAB syntax (for convenience and brevity),
What does ...
4
votes
1answer
212 views
Calculating phase response of maximum phase filter using Hilbert Transform
Given only a magnitude response $A(\omega)$ of a minimum phase filter, one can calculate the phase response using the Hilbert Transform:
$$θ(ω) = -\mathcal{H}\{\ln(A(\omega)\}$$
This paper suggests ...
0
votes
2answers
4k views
Plotting the magnitude response of a filter?
I have designed a second order butterworth filter.
Sampling frequency: $4\textrm{ kHz}$, Cut-off frequency: $500\textrm{ Hz}$
$$e = \tan\left(\frac{\pi \times f_c}{f_s}\right) = \tan\left(\frac{...
0
votes
1answer
60 views
Does a filter need to completely attenuate high frequencies to be considered low-pass?
I'm looking at a system with a frequency response that is: $$H(e^{j\omega})=\tfrac{1}{4}(2\cos(\omega)+\cos(2\omega)+2)$$
I think the magnitude of this system looks like this (not sure what is the ...
0
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1answer
619 views
When does the Amplitude Spectrum equal the Magnitude Spectrum?
I had the following question on edX:
I'm failing to understand why the second signal has $M(\omega)=A(\omega)$. First I find the DTFT of the signal:
$$\mathcal{F}\{\delta [n]+\delta [n-1]\}\ =\ ...
1
vote
1answer
1k views
Magnitude of function in $z$ domain
I am newbie to $\mathcal Z$-transform, I searched to find the magnitude of a function in $z$-domain, but I couldn't find anything, for example when we have
$$
H(z) = \frac{z-3}{z-0.5}
$$
How do you ...
1
vote
1answer
490 views
How to reconstruct signal of its phase and magnitude functions?
I have two continuous periodic (a period of $2\pi$) functions which belong to the phase and magnitude of Fourier transform of a signal, how can I reconstruct the original signal? What kind of ...
3
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1answer
3k views
How does zero-padding affect the magnitude of the DFT?
Let's simulate sinusoids of two frequencies using the following Matlab code:
...
0
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1answer
366 views
Recovering signal from magnitude and phase of FFT
I'm trying to code the basics of an analysis-synthesis system on MATLAB, but I'm getting incorrect results. From the Wikipedia page:
$$
X_k=\lvert X_k\rvert e^{i\angle X_k}
$$
Here's a simple MATLAB ...
0
votes
1answer
1k views
Bode plot of discrete-time transfer function $H(z)$
$H(z)$ is the transfer function of a biquad filter as described here.
I would like to plot the Bode plot of the magnitude response of $H(z)$.
Scipy has a bode method (...
0
votes
2answers
17k views
How to plot magnitude and phase response by hand if I have the Transfer Function?
I have the transfer function of the system, which is:
$$H(z) = \frac{1-z^{-1}}{5(1+2z^{-1})}$$
How do I sketch the magnitude and phase response?
I'm sorry for the bad formatting, it's my first time ...
0
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0answers
55 views
Obtaining a frequency response from other frequency responses
I have loaded six impulses responses (1024 samples each in length) into Matlab, zero-padded the end of each with 1024 zeroes and taken 2048 point DFTs of each using Matlab’s built in ...
1
vote
1answer
331 views
How can resonance be added to a fractional order Butterworth low pass
I am interested in how to add resonance (Q) to the magnitude response of a Butterworth low pass when it is expressed in the form:
$$
G^2(\omega)=\frac {1}{1+\left(\frac{\omega}{\omega_c}\right)^{2n}}
...
-1
votes
1answer
146 views
How to implement Cross Spectral Density [duplicate]
I am writing a program to compute the cross spectral density of an image, and a template image, which is the image I am trying to find in other image.
Reading wiki1,wiki2,wiki3 from wikipedia, and ...
4
votes
1answer
8k 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 ...
0
votes
1answer
123 views
Converting magnitude to dBs
I have seen people using 10*log10 and/or 20*log10 while converting magnitude to dBs. What are the differences and which one is valid?
0
votes
1answer
199 views
Amplitude of an image
If I take a two dimensional image and conduct a fourier transform on it, I would get a two dimensional matrix of complex values. If I want to find the amplitude of each value, is that the same as ...
4
votes
2answers
29k 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?
0
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4answers
958 views
Coherence vs. Magnitude Squared Coherence
currently I am writing my masther thesis. The theory part is about the turbulent wind field generation, where the coherence (not magnitude squared) is used:
$$\text{coh}(f) = \frac{|P_{xy}|}{\sqrt{P_{...
0
votes
1answer
73 views
zero-phasing frequency components while keeping the same magnitude, in Matlab
How is it possible?
I was thinking of taking just the real part of the DFT of my signal (isn't that zeroing out phases?) with
real(fft(X))
but the magnitudes ...
0
votes
2answers
323 views
phase, magnitude, audio file and information
I've been doing some thinking lately. I know that for image files a larger portion of information is contained in the phase of the signal. How does that go for the audio? Does the same hold or is the ...
-1
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3answers
1k views
MATLAB frequency magnitude spectrum
I am using the following code to generate four sine waves using a sampling rate of 8000.
...
0
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1answer
117 views
Sketching Phase Spectra Using Group Delay and Magnitude Spectra Informations
I have only magnitude spectra and group delay information and I need to sketch phase spectra from this information. For example, group delay is given like this: $\tau_{g}(\omega) = c$ where c is a ...
1
vote
2answers
341 views
Averaging Multiple Magnitude Spectra
I'm currently trying to implement some of the methods found in this paper on intelligent equalization - http://www.aes.org/e-lib/browse.cfm?elib=16792 -
The first part of the process is to build a "...
1
vote
3answers
35k views
How to compute magnitude and phase response from transfer function in Z-domain?
I have a transfer function $$H(z)=\frac{1+1.2z^{-1}+0.8z^{z^-2}}{1-0.9z^{-1}}$$ from which I'm supposed to sketch the magnitude and phase response. I know that you can transform $z=e^{j\omega}$ to get ...
2
votes
1answer
15k views
Energy calculation in frequency domain
I was just wondering... The formula I learned to calculate the energy of the signal is expressed in the time domain:
$E_x^{\text{time}} = \sum_{n=-\infty}^{\infty} |x[n]|^2 $
Then, what does the ...
0
votes
1answer
599 views
sketching magnitude of frequency response of H(z)
I am trying to plot the magnitude of H(z), I got it to factore, and would like to sketch its plot of magnitude. But I am have trouble evaluating the function.
$$
H(z)= \frac{(1-2z^{-1})(1+0.5z^{-1})(...
0
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0answers
775 views
fft magnitude scaling
I use the following code to calculate the fft of 1024 samples of a 200 Hz windowed sinusoid (code taken from aurio touch apple example app):
...
0
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1answer
162 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 ...
0
votes
2answers
957 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 ...
3
votes
3answers
3k 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 ...
0
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2answers
166 views
how to make fft ignore phase shift when only interested in magnitude
I have a signal that consists of a sine wave, on which I apply a rectangular window and then an FFT. I'm only interested in the magnitude of the sine wave, and I want it to stay the same even if the ...
0
votes
1answer
239 views
Change of bin magnitude when phase of signal changes when doing FFT?
I am working on an implementation in which I need to apply an FFT to determine which of 4 frequencies are present in a signal.
I am doing a 64 point FFT on a buffer which only is partly filled (the ...
1
vote
1answer
165 views
Obtaining the magnitude of the frequency response by plugging $e^{jω}$ into the z-domain transform function?
I am reading a text on discrete signal processing, which states that the frequency response of a signal can be obtained by plugging the value $e^{jω}$ into the z-domain transfer function $H(z)$. In ...
16
votes
3answers
6k views
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 ...
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0answers
166 views
Constant phase for each frequency?
FFT of some signal $x$ has two parts: $|x|$, which is the magnitude spectrum and $arg(x)$, which is the phase spectrum. I want each frequency to have the same phase. Is there a way to accomplish this?
2
votes
1answer
402 views
Plot Magnitude from RBJ Biquad
Currently I'm working out plotting biquads in a VST/AU plugin and have problems with the graphics part. I posted in several forums but haven't got a really useful answer for this case.
First, tell ...
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0answers
264 views
IIR: get magnitude and phase from coefficients
i'm trying to plot 1)the magnitude and 2)the phase response of an IIR eq with only its coefficients.
i've found somewhere that one can find the magnitude response starting with the transfer function :...
3
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3answers
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?
...
1
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1answer
4k views
retrieving original data from phase and magnitude of Fourier transform
I use this snippet of python code to transform data to Fourier phase and magnitude and then retrieving original data.
...
