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2answers
35 views

Compare between JPEG and JPEG2000

JPEG image compression is Fourier based DCT while modern image compression technique like JPEG2000 is based on more multi-scale technique like Wavelets.I want to know how Fourier and Wavelets are ...
1
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1answer
28 views

List of Fourier coefficientes to simulate musical instruments

I'm trying to find a list of Fourier Coefficients (frequencies/amplitudes, ie, spectral data) to simulate different musical instruments using additive synthesis. Are these data published somewhere? ...
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2answers
43 views

Find the Differential Equation of an Analog Band Pass Filter

I don't even know how to start. We're supposed to find the differential equations that links $V_{in}$, $V_{out}$, and $V_{io}$, as well as the values of $C_1$, $C_2$ and $R$ so the filter works in the ...
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1answer
103 views

Shift in Time-Domain after FFT-Convolution

To my understanding, multiplying a signal in the frequency-domain is equal to a convolution in the time-domain. I wrote a small python program, but i always end up with a shift in the time domain. ...
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1answer
38 views

Power Spectral Density computation and units

I want to make some calculs of power spectral densité of signal. For example a real voltage signal (physical unit : $V$) in time $g(t)$, its fourier transform $G(f)$ and $S_g(f)$. As far as I ...
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0answers
74 views

Sampling Continuous-Time Signal

This my homework: Input signal to system is: where H(exp(jw)) is transfer function of ideal low pass filter with cutoff frequency wg=3*pi/4 and zero phase characteristic. Sampling in A/D ...
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2answers
59 views

Frequency spectrum of signal - Matlab

Here is the code I use to plot a function in frequency domain in Matlab: ...
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0answers
23 views

Fit a plane on a 2d picture

My supervisor gave me the hint, to fit a plane on a 2 dimensional image and substract it from it before doing the fast fourier transformation to reduce low frequencies. I get the low frequencies ...
0
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1answer
65 views

Increasing the number of points in the frequency spectrum

I have an image with few pixels in length and height. For this image I calculated the two dimensional Fourier transformation. What I got for the frequency spectrum in one direction was a very ...
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0answers
39 views

Most efficient phase linear x4 resampling algorithm

I'm working on a program in which I need to do the following about 20 times for each block of audio: - Upsample from 192 to 768 kHz (x4) - Clip - Downsample back to 192 kHz (/4) What I'm using now: ...
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0answers
23 views

energy and power type signals [duplicate]

How can I determine if the signal $$\begin{array} \\g_1(t)=A\cos (2\pi f_c t), & \frac{-T}{2}<t<\frac{T}{2} \\ 0, &\text{otherwise} \end{array}$$ and: $$g_2(t)=\cos(t), -\infty < ...
2
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1answer
86 views

Signal Processing using Fourier Transform

How can I derive the fourier transform of ...
0
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2answers
106 views

Instantaneous magnitude

I was reading this thread: How to get Instantaneous Magnitude for a Instantaneous Frequency From FFT? I have basically the same question, but I'm curious about more detail about the Hann window ...
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2answers
91 views

A clarinet has no even harmonics. What would produce no odd harmonics?

According to this link, the waveforms of clarinets do not have even-numbered components in their harmonic series: A closed cylindrical air column will produce resonant standing waves at a ...
0
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1answer
55 views

Filtering Passband Signals using Complex Baseband Filtering

So I'm given a pass band filter with specific transfer function $H_p(f)$, I want to implement this via baseband processing. I already know how to take the input signal $u(t)$ and process it such that ...
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0answers
12 views

Creating synthetic frequency domain box filter vs 4 pixels in corners

Creating two 10x10 black images. 1st image, adding a 2x2 white box in the middle (Low pass filter). 2nd image, adding 1 pixel in each of the corners. Then performing the following steps in that ...
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2answers
134 views

Essential Bandwidth of rect(t/T)

Here is a question I have been trying to solve: Estimate the "essential bandwidth" of a rectangular pulse $$ g(t) = \operatorname{rect}\left(\frac{t}{T}\right), $$ with $T>0$, where this ...
2
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1answer
116 views

Regarding Bode plots; $H(s)$ and $H(j\omega)$

In circuit analysis, I understand the use of Laplace Transforms to obtain the impedance of a linear RLC circuit, ie transforming from the time domain to the frequency domain. In most texts I have seen ...
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0answers
28 views

Calculating energy spectral density?

For surface of self-windowed function $x_x[n,k] = x[n]x[n-k].$ I can think to make two fourier transforms, one over $n$, and one over $k$. Question: Can anyone highlight an interpretation of each? ...
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1answer
84 views

What's the essential bandwidth of the unit step function?

The Fourier spectrum is in the Figure, how to find the essential bandwidth?
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3answers
130 views

Study Signal Processing

I'd Like to ask two questions : What is the difference between studying Signal processing (both Deterministic and statistical) in Department of Electrical Engineering versus Department of Mathematics ...
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1answer
87 views

FFT on XY data points [closed]

Are there any algorithms out there that can do a FFT of 2D or XY data (not sure of the exact terminology here), I don't mean XY data like in a graph I mean XY/2D data points like a circle or a smiley ...
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0answers
94 views

Using Fourier Transform on Gyroscope

The original idea is to calculate distance from accelerometer input. However, accelerometer reading also contains the gravitational values, thus to remove gravity, I tried using Gyroscope. The idea ...
1
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1answer
366 views

FFT Matlab - Meaning of Frequency Vector

I'm following a tutorial about the FFT. It's well explained but I don't understand the meaning of the frequency vector: ...
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0answers
156 views

Extraction of fundamental signal information-Fourier full cycle algorithm

After filtering my noisy input signal using an anti-aliasing and FIR filter, I now wish to get the basic signal information (peak voltage and impedance; $R$ and $X$) from the pre-filtered as well as ...
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2answers
147 views

Intuitive explanation of the Fourier Transform for some of the functions

Does anyone have a mechanism to understand intuitively (and automatically) why the Fourier Transform of certain functions have certain shapes (at least for some functions, not necessarily for all)? I ...
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2answers
117 views

Frequency spectrum of a sinc function

I am doing one example from my book as a preparation for exam. The assignment is: It is given that: $$\mathbb{rect}(t)=pf(t) \leftrightarrow PF(f)=2AT_0 \cdot \mathbb{sinc}(2\pi fT_0)$$ you ...
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1answer
85 views

Polarity inversion in frequency domain (polar coordinates)

I don't fully grasp how polarity inversion is performed in the polar coordinates of frequency domain. The frequency components of the signal do not change, so the amplitude part is going to stay ...
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2answers
140 views

Properties of Spectral Transformations - Allocation (decomposition into even and odd part)

I am trying to understand the Allocation property of Spectral Transformations. I can't. I know that every function can be separated into an even part and into an odd part. My problem is ...
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2answers
64 views

Fourier Transform Time Scaling

I edited the initial question to make it general and thus applicable in more situations. If the Fourier Transform of $x(t^2)$ is some function of $\omega^2$. Then what is the Fourier Transform of ...
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0answers
38 views

increase the # of points in a DFT, increase the processing

I have a question which is closely related to this one: FFT Processing Gain ^that discussion is a bit general so I want to ask a very objective question to see if I can apply that knowledge: If I ...
0
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1answer
98 views

Phase information

I am quite new to MATLAB and I am currently trying to do some Fourier synthesis. In order to do the Fourier synthesis I need the phase information of the harmonics as a fraction of the period of the ...
0
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1answer
34 views

Reason for bimodal behavior while low second fourier coefficient

If I have a time series (for eg. for 23 timestamps) and if I plot it and see that it is bimodal, that means it might be having high value of second fourier coefficient (with frequency = 2). But when I ...
0
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1answer
38 views

How to check if Fourier components are in phase of out of phase?

I have a time series (of 23 timestamps) of which I take the Fourier transform. Now the fourier transform has 23 imaginary values and each has an amplitude and a phase. When I get the phase angle, it ...
1
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1answer
348 views

Computing narrowband spectrograms using MATLAB [closed]

I'm having an assignment of computing narrowband spectrograms using MATLAB. And I totally have no idea about the code. Can someone help me writing the code and explaining what's going on to me. Lots ...
1
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2answers
61 views

Complex numbers in a frequency domain of a 2D image [duplicate]

I am try to grasp the idea of frequency domain for images. I think get the basics, but now I've stuck with a question that I can't find appropriate answer anywhere. How are frequency domain and ...
2
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1answer
69 views

Is it possible to open up this particular convolution equation?

I have three vectors, $x[n]$, $w[n]$, and $z[n]$. I need to compute: $y[n] = z[n] * \Big(x[n] \cdot w[n] \Big)$. This is easy to do. However, is there a way I can do this by 'opening' up the ...
0
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1answer
48 views

How is the complexity of applying Short term fourier transform over n samples with a moving window of size m amount to O(nmlogm)

I have been trying to understand a publication here where Short time fourier transform is applied over n samples in steps of m samples each (m is the size of the moving window). I understand that the ...
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2answers
121 views

Convolution of an image with a kernel that is a product of two functions

Suppose that $G(i,j)$ is a Gaussian decay function on the distance between points $i$ and $j$ of an image. In addition, $D(i,j)$ is the difference between the VALUES of the image at those points. ...
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2answers
251 views

Frequency domain confusion

I'm a bit confused with some details about frequency domain or studying systems with Laplace and Fourier analysis. Let's say we have a system with a transfer function $H(s)$ with no poles and zero's ...
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3answers
192 views

Is sinusoids the nature's default signals?

I know the basic working principle of sinusoidal oscillators. But I have a doubt on this matter when I came across Gram-Schmidt orthogonalization procedure. I have read that the source for sinusoid ...
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1answer
110 views

g(x)=x odd and even expansions

I'm studying book about digital filter by Richard Hamming. And there is exercise to get odd and even expansion of g(x)=x where x is from 0 to $\pi$. I understood even expansion, but can't get into odd ...
0
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1answer
150 views

Discrete Fourier Transform bandwidth?

In a problem I'm working on, I have a signal that is sampled 256 times for 3.5 microseconds. After performing a Discrete Fourier Transform on the data, what is the frequency step between the ...
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2answers
3k views

Obtaining the fourier transform of cosine and sine

In this answer, Jim Clay writes, use the fact that "$F\{\cos(x)\} = \frac{\delta(w - 1) + \delta(w + 1)}{2}$" The expression above is not too different from $F\{{\cos(2\pi ...
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2answers
2k views

For a LTI system, why does the Fourier transform of the impulse response give the frequency response?

I know that for a given system, the Fourier transform of its impulse response gives its frequency response. I want to find where this property comes from, but haven't been able to find if it's a ...
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3answers
2k views

How do you relate imaginary numbers with phase shift? How to imagine this?

So I found this answer on one of the questions. I wanted to ask how the complex part can be related with the phase shift. I wanted to ask this on the same question but it didn't allow me. Could ...
4
votes
1answer
206 views

Fourier transform of Autocorrelation function, what am I missing here? (Power spectrum)

Given this problem I know that the autcorrelation and power spectrum are fourier pairs, so when taking taking fourier transform of Rxx, one should end up with Sxx However, when I take the ...
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0answers
74 views

understanding windowed fourier ridges

I am studying windowed Fourier ridges for my project. I know that it computes the instantaneous frequencies and amplitudes from the spectrogram. But I don't really know how it relates to signal ...
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1answer
455 views

Example of Fourier Transform not existing for real-life signals?

I got curious based on this question here, but basically, is there ever a real-life signal that exists where its Fourier transform does not exist? If a signal is not finite energy, then its Fourier ...
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0answers
153 views

Points of interest in a spectrogram

We have several audio tracks, all of which are different versions of the same track under one type of distortion: the speed of the track is increased by a constant factor K (hence frequences are ...