Questions tagged [array-signal-processing]

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21 views

pattern recognition with some features in time series data

I am trying to capture peaks in a time series data which has some predefined feature. Here is a snapshot of time-series data (Time series data with peaks) In this time-series I want to detect peaks ...
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3answers
84 views

Convert a list of values and times into an audio file

I have two pandas dataframe, one with time in seconds and one with the actual audio data (values from -1 to 1). The audio data points are not equidistant, this why I need the list of time in seconds. ...
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32 views

What are some good examples of applications of Circular Convolution in Signal Processing and Image Processing?

I have derived the circular convolution property for an affine Fractional Fourier Transform and I need to work on an application for my research. Any idea?
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37 views

I have two signals, recorded from the same device. How do I standardize/normalise them?

I essentially have two signals X and Y, recorded with PPG devices. These have been filtered already. I want to standardize(z-score) or min-max scale them but I don't know if I should do this on each ...
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2answers
53 views

Discrete Wavelet Transform (DWT) and wavelet family

I have just started reading about wavelets for a data compression problem that I want to perform. I am reading about Discrete Wavelet Transform (DWT) but I can't understand where the wavelet family ...
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3answers
69 views

What does the intensity values on wavelet transform mean? Amplitude or power?

So when applying wavelet transform, we get a 2d plot. Each point in that 2d plot has a color, showing intensity of something. But I cannot understand if it is an amplitude or power?
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1answer
64 views

Can FFT tells us existance of same frequencies with different phases?

So I know that applying FFT on a time-domain signal, shows which frequency components exists and what amplitudes each frequency signal has. My question is, suppose the signal contains same frequency ...
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1answer
73 views

Extracting different frequency bands (alpha, beta, gamma) from MEG source estimated data

I have a dataset that consists of source estimated data of MEG brain signals. I need to extract the different frequency band features (i.e., alpha, beta, gamma, etc) from them. What steps/procedure ...
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1answer
45 views

Calculating power of brain signals

I have a dataset that contains EEG (or MEG) recordings of brain signals during some cognitive tasks. Each row, shows the source estimates of neurons in a particular region. source estimate contains ...
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2answers
289 views

Why does my amplitude change upon inverse Fourier Transform when I am only randomizing the phase of the fourier transform using Python numpy?

I am trying to make a surrogate time series of a discrete data series using python, basically I wish to keep the amplitude same and change the frequency I take a Fourier Transform of the data I ...
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2answers
99 views

How to reconstruct the signal using overlapping frames in MATLAB

I understand that we can use the buffer function in matlab to split a long signal into overlapping frames. But is there any functions that we can use to put the ...
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0answers
24 views

Filtering relationship for sources propagating over a sensor array

A sensor array $y$ measures the superposition of $N$ sources $s$, at time $t$ and position $x$ we have : $$y(t,x)=\sum_{i=1}^{N} s_i(t,x)$$ The sources $s$ travel at constant speed over the array of $...
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2answers
179 views

Why do we need to estimate eigenvalues?

I am not working in signal processing field, but recently I happen to read a paper which estimates source numbers using Gerschgorin radii, and I feel kind of confused about why we need to estimate ...
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12 views

Correlated signal components from uncorrelated and incoherent source after reflection

To this point, it has been assumed that the point sources composing the source are uncorrelated, generating fully incoherent signals. Thus, capturing the reflected signals and after sufficient time ...
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0answers
31 views

Beamforming and AoA with a small number of elements

So I have an antennae array with only three elements. I want to know what kind of beamforming and AoA estimation I can do with such a small number of elements. I understand that there are lots of ...
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1answer
55 views

Visualise/compare numpy arrays from Matlab/Octave to matplotlib

I'm new to python and matplotlib, and I'd like to visualise / compare 3 mfcc files stored as numpy arrays in txt format. I have the Octave code below, and I'd like to know how it can be done using ...
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0answers
74 views

Signal-to-Noise ratio of multivariate stochastic process from Correlation Matrix

I'm not in signal processing, I'm from an another discipline. I've derived a simple result which I presume must be well known in SP and I'd like to know whether there's a paper or textbook that has it ...
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1answer
108 views

a neural network approach for FIR filter

I am trying to write a code for a neural network to do the digital filtering on some signals. Is there any neural network model for digital filtering?
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0answers
65 views

Spatial moving average in array antenna processing

In array processing the theoretical spatial response of the array is calculated by doing DFT on sensor locations for some assumed wave number (1/wavelength). The figures below shows the sensor ...
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1answer
113 views

Cross-correlation of two signals

I want to find the direction of a sound source in 2D space. I use two microphones and one sound source for that. I have recorded audio data into two arrays. When a sound is detected, it starts to ...
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44 views

What is Ad-hoc microphone array?

I have stumbled upon this term in many papers, though no one bothers to elaborate. Is this the case where I do not have prior knowledge of the array structure? or otherwise is it the number of ...
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1answer
74 views

Discrete Signal Windowing

How do we apply windowing of 50% (4 samples) to a discrete signal with the odd number of values as 1234567? Is it done as: ...
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2answers
704 views

MUltiple SIgnal Classification (MUSIC) Implementation

I have a linear 4 element antenna array currently in my design, I am able to obtain the I/Q data from each antenna. Now I am trying to implement the MUSIC algorithm to obtain the AoA (Angle of Arrival)...
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21 views

When does the narrowband model in array processing fail?

I am not sure that I understand well the narrowband assumption in array processing. I wonder how it simplifies the model and what would change if not assumed. Also, what will happen if I apply the ...
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26 views

Calculate the percentage of accuracy with which user made the assigned sound

I want to design a web-app for my cousin who is 2 years of age in which i have implemented a functionality in which when an image is clicked some sound gets played and the user has to make the same ...
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1answer
284 views

Zero peaks in fft data even after subtracting mean

I have a time series sensor data. It is for a period of 24 hours sampled every minute (so in total 1440 data points per day). I did a fft on this to see what are the dominant frequencies. But what I ...
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1answer
3k views

Python code for QPSK modulator [closed]

Have any of you done anything like QPSK Modulation in python? I am in the middle of it and having problems in setting up bits? like odd and even bits. Have you got any idea? Regards, Sam
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1answer
110 views

Question about eigendecomposition, signal subspace and their properties

Lately, I am readig a paper titled A Subspace Method for Estimating Sensor Gains and Phases. In it, it is mentioned: There are $m$ sensors in the array, $n$ known narrowband far-field signals($m \...
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1answer
226 views

Source Localization with the BLUE Estimator

I'm trying to implement BLUE estimator in MATLAB for source localization and after my research I've come up with a theoretical example in Steven Kay's "Fundamentals of Statistical Signal Processing: ...
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0answers
54 views

Sign of manifold vectors in monostatic phased-array radar

I am reading some notes where the impulse response of phased-array to is given by; $$ \beta S(\theta, \phi) \bar{S}^H(\theta, \phi) \cdot \delta(t-\tau) $$ where \begin{align} \bar{S}(\theta, \phi)...
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1answer
245 views

Detect when signal starts oscillating

I have a signal which consists of oscillations riding on square waves as shown in the image below. I wish to detect the time at which oscillatory events occur (as shown by the red star). Each square ...
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1answer
176 views

How do I create a polar plot from a multi-channel sound file?

I have a multi-channel sound file from a microphone array. I want to get the polar plot in Matlab in order to get the directivity patter of the sound source. How do I do this? I did the FFT on the ...
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1answer
610 views

Radar signal processing flow chart

I'm new to Radar in general, and I'm studying RADAR using online resources. I came across the following slide which shows the process flow of the Radar signal processing. The thing I don't get in ...
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0answers
110 views

How to compare imaginary coherence values?

High, I am currently writing my Master's thesis on susceptibility for hypnosis. I am comparing EGG signals of lowly and highly susceptible individuals. The imaginary coherence is given by: $$ \...
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26 views

Temporally synchronize two different or more real time digital audio signals

Are there any DSP techniques to temporally synchronize two different or more real-time digital audio signals without timestamp information?
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1answer
29 views

Arbitrary shaped RIR generator

I wish to simulate some sound sources convolved with a Room Impulse Response (RIR) and impinging on a spherical microphone array. I could find a couple of generators online (such as this one), though ...
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1answer
64 views

Is it possible to estimate the DOA from real samples only?

I'm sampling a ULA with a scope after transmitting a CW. I'm wondering if I can estimate the DOA assuming I'm interested only in the range [0,90] [deg] and not the full [-90,90] [deg]. The first issue ...
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1answer
58 views

The frequency-domain spectrum obtained using MATLAB's FFT function seems inaccurate

I am using MATLAB R2018b on a Windows 10 PC. In order to obtain the frequency domain information of a signal, I'm applying MATLAB's FFT function. The signal of interest is obtained from an experiment ...
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2answers
138 views

Number of microphone limitation for Spherical Harmonics based DOA estimation

I am following this book "Theory and Applications of Spherical Microphone Array Processing", as well as this paper on DOA estimation "Eigenbeam-ESPRIT for DOA-Vector Estimation". My dataset is ...
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0answers
25 views

DOA estimation of moving, radiating source in the near-field with nonuniform Doppler shifting

I am trying to estimate the DOA of a radiating source using two passive sensors. In the case of a stationary source, I find the lag $k$ of the maximum in the sample cross-covariance sequence $E \...
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0answers
46 views

How to crop a song and mantain the same values in the sample vector?

Does anyone know how can I crop an audio signal and maintain the same values in the sample vector? I am working on a audio signal processing project for song recognition in Python and I wanted to ...
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0answers
33 views

Blind source separation from microphone array

I was following this article and I wanted to "borrow" their Idea for my own work. The difference is that I am using a microphone tetrahedral array and not a binaural microphone. I have two different ...
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2answers
88 views

Convolution property

Is the convolution of two equal signals the same signal? I have this system: and i have to find $h_1[n]$ (which i've been struggling for a while), given $$ h_2[n] = u[n] - u[n-2] $$ and $h[n] = ...
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5answers
2k views

Multi-channel audio upsampling interpolation

I have a four-channel audio signal from a microphone tetrahedral array. I wish to upsample it from 48 kHz to 240 kHz. Is there a preferred interpolation method for audio? Does cubic ...
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2answers
345 views

Tetrahedral microphone array beamforming

I have a microphone array of 4 channels taken as channels [6,10,22,26] from Eigenmike spherical microphone array. I wish to do 3D beamforming and create $8\times 4$ beams, 4-elevations with 8 ...
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2answers
599 views

Delay in Savitzky-Golay filtering

I am applying a Savitzky-Golay filter to a signal, using the scipy function. I need to calculate the lag of the filtered signal, and how much is it behind the original signal. Could someone shed ...
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1answer
135 views

By using array antenna and a MUSIC algorithm, how many targets could be detected?

By using an array antenna which has N receivers, How many targets could be detected and classified when we use the MUSIC(MUltiple SIgnal Classification) algorithm?
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1answer
32 views

Feature normalization (scaling) for Hyperspectral images

have been straggling with the concept of feature normalization for the hyperspectral images. Respect to my problem I have attached a picture of my problem which clearly stands the issue which I have.
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0answers
39 views

Excluding points too close to a set of coordinates

I was wondering if anyone can help me. My ultimate aim is to take an image like the one shown and draw line between the white and black blobs that show a direction and output the coordinates in the ...
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1answer
182 views

Separating two frequency component

How can we separate two frequency component when they get mixed means when signal get mixed with noise how receiver can judge which part is signal and which is noise ?