All Questions

4
votes
2answers
422 views

Fourier Transform with both Time Delay and Frequency Shift

I know that the Fourier transform of a function with time delay can be written as: $$\mathscr{F}\big\{x(t-t_0)\big\}=X(f)e^{-j2\pi f t_0}$$ The Fourier transform of a function with frequency shift ...
0
votes
1answer
44 views

Digital filter design of time series for specified frequency response function

I am currently working with vibration measurements in structures. In the netherlands there is a guideline for verifying vibration measurements for damage to machinery. This is the so-called "SBR ...
1
vote
1answer
16 views

Sampling Frequency and Spectral Regrowth

Sampling a cosine wave of 10 Hz at Fs = 64 and number of samples Ns = 256 I setup my time vector for the cosine wave as n=(0:Ns-1)*(1/Fs) If I change the sampling frequency from 64 to 64.0005 I get ...
0
votes
2answers
39 views

Correlation between 2 signals of uneven dimensions

As a part of my work, I am trying to correlate the audio signal in a video with the pixels of each frame. The steps I follow are: Audio sampling rate and frame rate of the video are known. So, ...
2
votes
1answer
60 views

Simulate time series given temporal auto-correlation functions

Given a random process $x[n] \in \mathbb{R}$ (say of length $N$) and all correlation functions such as: \begin{align} \langle x[i]\rangle\\ \langle x[i]x[j]\rangle\\ \langle x[i]x[j]x[k]\rangle\\ \...
0
votes
0answers
20 views

Determine filter type using recurrence relation

Given the recurrence relation: $y[n] = x[n] + 0.5y[n-1]$ I want to determine the filter type (i.e. LPF, HPF etc.) I try to use Z transform, and get that the the transfer function is $H(z) = \frac{2z}{...
5
votes
3answers
204 views

Deconvolution of Synthetic 1D Signals - How To?

I convolved a square wave with a Gaussian wave using linear convolution. Can I get the original square wave back by deconvolving my output with the Gaussian function? I took the FFT of both signals, ...
0
votes
1answer
28 views

In OFDM, what is the length of the cyclic suffix that is added before windowing?

I searched for length of cyclic suffix but all I can find information about is the cyclic prefix, I want to know also if there is short guard interval and long guard interval does it affect the length ...
1
vote
0answers
30 views

How does a Costas Loop lock to one of multiple BPSK signals

I've been looking into how GPS receivers work in terms of signal processing. When a GPS receiver tracks the received signal, it often uses a Costas loop to synchronize the carrier. How that works ...
0
votes
1answer
41 views

Confusion about ensembles and averages in autocorrelation matrices

I just noticed that until now I often don't cared about the scaling of the autocorrelation Matrix in Matlab. I then checked with the book Statistical Digital Signal Processing from M. H. Hayes. There ...
1
vote
2answers
99 views

Solving a Linear Mean-Square Estimation the easy way

I have an exercise which is quite trivial. However I got stuck and I'm not sure if this the end-result. I assume there has to be a way to get this result much quicker. Given are two randomly ...
-1
votes
4answers
91 views

What are real-valued and complex signals and why is the Fourier transform of a real-valued signal Hermitian?

I have confusions in these concepts: What are real-valued signals? What is the difference between it and complex signals? Why is it so that for real-valued signals, the spectrum of negative ...
1
vote
0answers
19 views

Why is my resampled signal cutoff when resampling with a windowed FIR filter in MATLAB?

I have an exercise to write a function which upsamples or downsamples a signal by a factor of F (integer) using a FIR filter windowed with a Kaiser window function. Exercise I had last week included ...
5
votes
1answer
70 views

What type of low-pass filter to use for gyroscope filtering in control application?

I am using a gyroscope to generate a feedback signal that drives a motor to resist rotation, just as in a camera gimbal. The gyroscope is sampling at 32 KHz with a bandwidth of 8 KHz, and my control ...
0
votes
0answers
49 views

tensor flow is slow on gpu

I'm trying to do people detection using tensorflow. Here is a video of what I came up for https://youtu.be/93XOujVi-1U My questions. I run the tensorflow on GPU 1050ti nvidia, and it's extremly ...
1
vote
0answers
36 views

What are the differences between Gaussian down-sampling and bicubic down-sampling in Matlab? Which is more accurate for simulating low resolution?

I see in some of the technical papers, good practice for downsampling is to first pass the image through a Gaussian Filter and then take sampling to avoid problems like aliasing and so on. However, ...
1
vote
2answers
46 views

Wavelet is a small wave, what is problem with using sin(x) of one cycle?

As far as I know a $\sin(x)$ which is one cycle long can be made into a wavelet and then we can use its dilated and translated versions to represent another function, effectively a wavelet transform. ...
0
votes
0answers
21 views

Why are patterns repeated in the frequency-power graph of a periodic signal?

The original question was posted here. I have a signal, which I'd like to treat as a non-continuous function now, let it be $signal(t)$. It looks like this: Zoomed in a bit: I create a Lomb-Scargle ...
0
votes
1answer
23 views

Clarification on the application of window pre-FFT

Good morning, I have a simple question about the application of a Hanning window before performing an FFT. My application is pretty textbook, i'm decoding a 4-FSK signal. Question: why does the ...
-1
votes
0answers
6 views

Can anybody explain the difference between SIFT and GLOH image descriptors

There are very few resources on GLOH (Gradient Location and Orientation Histogram), Can anyone explain how is it different from SIFT?
1
vote
2answers
53 views

What is the meaning of positive and negative shift in signal correlation?

If $x(t)$ and $y(t)$ are real valued signal then from this page cross correlation between them is defined as \begin{align} R_{XY}(\tau) &= \int_{-\infty}^{\infty}x(t)y(t-\tau) dt\quad\text{+ve ...
0
votes
1answer
14 views

Error analysis for uniform quantization of uniform input

I was told that error energy $$\delta^2_e=\Delta^2/12,\quad \Delta=(B-A)/2^R$$ signal energy $$\delta^2_x = (B-A)^2/12$$ Here signal bounded:$A\le x[n]\le B.$ $[A,B]$ is split into $2^R$ ...
0
votes
0answers
21 views

Multipath propagation: pass loss [on hold]

1) I read that the path loss exponent depends on an height of antenna, frequency, polarization, climate. And also the post Question about path loss exponent estimation from measurment Ms MBaz wrote ...
0
votes
0answers
31 views

Matlab: How to implement expectation of product of hermitian matrix

I want to implement the following equation in Matlab: $\mathbf {R}_\mathbf {z}^a(\tilde{f}) = \mathbb {E} \left[\mathbf {z}(\tilde{f}) \mathbf {z}^H(\tilde{f}+a) \right]$, $ \tilde{f} \in \left[0, ...
0
votes
0answers
19 views

Synthesizing a function from a fourier transform

So I have this question in a homework and cannot seem to solve it no matter what I try. Question: Use Matlab to find out what function in time x(t) resulted in the Fourier Series ...
0
votes
1answer
20 views

how to lower frequency of a soubd file in matlab?

I am new to programming and sound processing, I have been using matlab to process sound files, a few of which are ultrasonic. my sampling rate is 250kHz. I Would like to be able to play the sounds at ...
0
votes
0answers
25 views

Autocorrelation

What is autocorrelation in real life? Any example? How does autocorrelation dependent on time difference? Here is Xt1 and Xt2 how comes \phi{tau}?
0
votes
1answer
31 views

DFT of a series of RC exponentials

Context: I'm trying use matlab to apply a single-pole filter to a time-domain ramp waveform that is generated by a sequence of time-shifted "RC steps" that are added together. The time domain voltage ...
1
vote
1answer
77 views

How can I improve my fit of cosines to periodic data using Python?

I have a space-separated csv file containing a measurement. First column is the time of measurement, second column is the corresponding measured value, third column ...
0
votes
1answer
35 views

Why is the size of results from FFT half the size of the input, while that is not the case in image processing?

When dealing with real data, Fourier Transform produces symmetric results and FFT algorithms discards half of it. An input with 1024 points will yield only 513 points in the output. However, in image ...
0
votes
0answers
28 views

vibration analysis in spherical coordinates

I'm trying to understand some data from a vibration sensor, in units of milli-g and in cartesian coordinates. One idea I had was to analyze the data in something like spherical coordinates, to ...
-1
votes
0answers
9 views

How to define and use custom wavelet filters in python?

I would like to define custom analysis and synthesis filters for wavelet implementation in pyhton. How it can be cone using pywt library?
0
votes
1answer
26 views

Designing Rayleigh Fading Wireless Channel with particular properties [closed]

I have some information on particular wireless channel between an Access Point(AP) and K users as described in the picture below: How i can create this channel in Matlab?
0
votes
1answer
17 views

response of LTI system to a Random Input Signal

what is LTI filter? what is the output when x(t) is input? let x(t) be the input signal to the system and y(t) denote the output signal. The output of the system may be expressed in terms of ...
0
votes
0answers
20 views

Artifacts observed in STFTs computed with C++ library FFTW3 or NE10

In one of my projects, I have to compute stfts with audio signals coming either from a microphone or a .wav file in a C++ based program. However, I am observing different artifacts due to my stft ...
1
vote
0answers
20 views

How to obtain the steady state response of the sampled periodic signal data?

Below the green plot Vin is 5Hz sine voltage signal from a function generator output sampled at 12kHz sampling rate: The blue plot Vout is the processed/filtered data by using the following code in ...
0
votes
0answers
12 views

GLP type three filter of order k, amplitude response?

Given a GLP type three filter of order K, with an amplitude response of |H(theta)|. I need to show that the number of real and causal FIR filters(identically different) of order K, with the same ...
0
votes
2answers
24 views

Frequency Resolution Problem

Im trying to tackle the following problem while still not having a firm idea on what "frequency resolution" means : Suppose we sample a continuous time signal with sampling period Ts = 1/2000, and ...
0
votes
0answers
17 views

Linear equation set construction for Brox et al. optical flow optimization

I'm trying to implement an optical flow calculation program for two successive images based on this article by Brox et al. The Euler-Lagrange combined with a fixed point iteration loop yields two ...
0
votes
0answers
10 views

Edge detection for bio-film filaments

I have this image of bio-film filaments growing in a matrix and would like to extract just the filaments from the image to calculate the angle at which they are growing. What techniques would be best ...
0
votes
1answer
24 views

Active Noise cancellation for non periodic signals

I observed that the coded algorithm for active noise cancellation is not able to cancel some of the signals like a human voice. Is there any solution for this? Can we really cancel non-periodic ...
0
votes
0answers
18 views

Wide-Band Lorentzian FDTD Algorithm

I want to convert a simulated gain/absorption of a material, which can be understood as a discreet (dispersive?) function $g_i(f_i)$ ($f$ is for frequency) or $g_i(\lambda_i)$, into $\tilde g(t)$ for ...
0
votes
0answers
14 views

Wifi signal stability of routers

In certain routers, there is a setting that allows one to change the interference resistance, which is bounded between the limiting cases of "maximum stability" and "maximum performance." Apparently, ...
0
votes
0answers
15 views

Services for phoneme recognition?

I wonder if anyone can point me to services or dev libraries that focus on or suit phoneme recognition? Target audience is children at learning to read stage. We have trialed IBM Watson (not good) ...
0
votes
1answer
29 views

periodicity of constant discrete time signals

are constant discrete time signals periodic? example \begin{equation} e^{i10\pi n} \end{equation} my proffesor says that this signal is aperiodic, in the discrete sense. but it seems wrong, because ...
2
votes
1answer
21 views

Error due to downsampling an image

I have two images $I_1$ and $I_2$ suppose $I_2 = downscale(I_1)$, so for example if $I_1$ has resolution 1024x1024 $I_2$ could be 512x512. How can I measure how much quality I've lost during this ...
1
vote
2answers
143 views

A question on Fourier Series and the frequency of the sinusoids

On studying about Fourier series, I encountered 2 doubts: How is it that a non-periodic function has a Fourier series? When expressing a periodic function as summation of sinusoids, why is the ...
1
vote
2answers
24 views

DFT sample point k < N has negative frequency

(From: Schaum's DSP outline, 2nd edition, page 254, problem 6.35) A signal $x_a(t)$ that is bandlimited to 10 kHz is sampled with a sampling frequency of $f_s = 20$ kHz. The DFT of N=1000 samples of ...
1
vote
1answer
82 views

How to get the background noise of microphone?

I am working on the automatic volume control for television which should take care of background noise. For this, I need to first find out the background noise. I have read in research papers that we ...
1
vote
0answers
42 views

audio sound localization using machine learning [closed]

I'm trying to localize a sound by using an array of microphones, the localization is done based on the sum and delay algorithm. I'm trying to to do the same in machine learning. I don't have much ...

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