Questions tagged [python]

Python is a high-level interpreted general programming language. Python has popular numerical and scientific libraries/packages, most notably numpy and scipy. The scipy.signal package is a powerful signal processing software collection. This tag covers the use of numpy, scipy, and other Python packages often used for SP computations.

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6 views

lopsided Hanning Window function

I am processing sensor signals and have been looking at using window functions to smooth out the signal before I conduct a fft on it. A normal symmetrical hanning function seems to disorientate the ...
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Zero phase - Minimum phase of Butterworth filter [closed]

I am trying to implement the Zero phase - Minimum phase of Butterworth filter (1st, 2nd, and 3rd order) from scratch using python. Based on the resulting plots, it seems that I am doing something ...
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1answer
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How to create a real bandpass filter?

I'm trying to create a real bandpass filter (17-point) in Python by calculating the coefficients b of a signal. This is the formula I'm using: $$b = \cos(ω(k-k_m))$$ for $k = 0,1,..,L-1$, where $k_m$ ...
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GNU Radio Stream Input-Vector Output

I successfully designed the transmitter block. I am now implementing the GNU Radio receiver block and using a Python (since it is easier for me to design a prototype) block that takes a stream of the ...
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1answer
52 views

Hankel Matrix SVD Denoising

I have performed Hankel Matrix Singular Value Decomposition de-noising to smooth out my univariate time series. It is the close price of EUR/USD exchange rate. Here is a picture: The problem I have is ...
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1answer
23 views

Creating the frequency-spectrum with VC-curves for Building Vibrations measurement

I'm very new to signal processing and can't get ahead: I'm using an Accelerometer to measure the acceleration of i.e. the building vibrations or elements/machinery etc. For creating the spectrum, I ...
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1answer
65 views

How to design a digital Butterworth bandpass filter?

I am looking into designing a Bandpass Butterworth filter in python, but, I was not sure I am designing my filter correctly. What I have are the following: High cutoff frequency = 200Hz Low cutoff ...
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1answer
25 views

Generate a PSF based on MTF Mapper's SFR measurement

Not sure if I should post this here or on Stack Overflow I have a .csv file from MTF Mapper with 2 columns from SFR measurement - frequency and contrast: ...
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1answer
48 views

Should i normalize FFT signal with z-score?

I am working with EEG data (time domain) in a machine learning task, where each input signal must be mapped to a class/frequency. I am using FFT in order to get data in frequency domain and make ...
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1answer
25 views

How to calculate magnitude of frequency response?

I'm trying to write a function in Python that calculates the magnitude of an FIR filters frequency response. I tried doing it by first calculating the Fourier transform with np.fft.fft and then ...
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How to find the shape of the highs from a noisy signal with many dips

I try to find that looks something like the red curve below and I am pretty clueless what is the best way. I tried first the Savitzky-Golay Filter, then I tried a simple fit with a second degree ...
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1answer
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Self-Adjoint Filter Doesn't Work

My understanding is that a symmetrical kernel is its own self-adjoint. For example, if we had the following kernel: ...
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How to do appcoef and detcoef using pyWavelets?

I am new to signal processing and currently doing a school project in wavelet transform using Python. I want to extract all details and approximations (Example: cA2, cA1, cD2, cD1), pywt could return ...
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Multilevel DWT wavedec - How to get each coefficient (approximations and details) in the same length as the original signal?

I am doing a school project referring to the research paper https://www.tandfonline.com/doi/abs/10.1080/0952813X.2013.813976?journalCode=teta20 The overall concept of the research is as the following ...
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1answer
56 views

inverse fourier transform coefficients

Context I want to implement (real) cepstrum on stock data (for example MSFT stock) and achieve cepstral coefficients of this time series. as noted in "Cepstral-based clustering of financial time ...
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1answer
24 views

Hop size in STFT

I am reading the documentation of scipy.signal.stft function: https://docs.scipy.org/doc/scipy/reference/generated/scipy.signal.stft.html#scipy.signal.stft. My question: is the 'noverlap' parameter of ...
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How to design function for Random Decrement technique in python and implement the function?

I was looking into a technique called Random decrement technique from the following links/articles: How can I use Random Decrement Method to convert a non-stationary signal into a decay function ...
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1answer
75 views

Implementing basic high pass filter using difference equation

For the following signal, I am trying to remove the gradual positive drift but retain the spikes using a high pass filter. I am aware that I can use implement a high pass filter using difference ...
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1answer
47 views

Send real and complex signal from python to GNU radio. ZMQ Python SUB -> GNU Radio

I've been reading about this. To do this, you should use the ZMQ blocks instead of the UDP blocks because of data loss. Now when using ZMQ I have problems with the received signal, if I create a np ...
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1answer
33 views

Fourier Transform High Pass Circular Filter Intuition

The situation I need to apply a high pass filter to an image. The approach I'm following uses Fourier transform to apply a circular filter which would eliminate low frequencies. Say I have a frequency ...
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48 views

High pass filter with specific cut-off frequency

The situation I am trying to apply a high pass filter to a black&white image to enhance the texture by keeping the high frequencies. The goal is to filter from a specific frequency value obtained ...
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1answer
56 views

Object Detection using audible sonar

I am currently working on a project of identifying the position and angle of the objects in an environment using sonar (audible) about 1 to 2 m away from a desktop speaker within an angular sector of ...
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1answer
56 views

Removing Attenuator and Real Mixer influence on the received Baseband signal in Radar IQ Transmitter - De-embedding

Radar IQ Transmitter Measurement Setup: Waveform Generator + IQ Transmitter + Attenuator + Real Downconversion mixer + Oscilloscope + Post-processing (Hilbert Transform) With the above arrangement ...
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Sample rate vs noise floor in power spectral density measurement

I am trying to measure the noise floor of my picoscope. I want to generate a PSD in volts per root hz that I can compare with specs from other equipment, e.g. a preamp. I gathered some data from my ...
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Separating several kinds of information in a sound file

I have a 90min audio recording of a lecture using a handheld recorder. Since the recorder was in the shirt pocket of the speaker, I can clearly hear that the their voice is much louder than the ...
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1answer
30 views

Detecting & tracking an arbitrary object in a video

I have a video from a fixed (stationary) camera. Sometimes there are slight movements in the frames (e.g. tree moving a bit in the wind). Other times, some might walk into the view of the camera, a ...
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3answers
396 views

Python FIR Notch filter applied on both + and - frequency but only need + frequency

I have posted a summary of what I am seeing, I just made a pulse train and testing a notch filter on it as an example only. I also have a complex baseband signal centered on 0 Hz, this complex ...
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1answer
19 views

Does BM3D really need the noise power spectrum beforehand?

I'm at the moment trying to implement a neural network which uses BM3D as a preprocessing step. The problem is, when using the python implementation of BM3D from the paper Collaborative Filtering of ...
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FFT filtering by hand in python - iffy issue - cannot get filtering right

I am trying to filter an image by hand (with no using the image processing libraries) to understand how fft.shift works in python. No luck. I take a png an image from MNIST, e.g.. Here is the code: <...
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Parameter tuning for noise removal in video frames background subtraction

I’m working on motion detection using video frames background subtraction. I already reached a good result by filtering detected motions area using thresholds where I keep only reasonable motions by ...
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2answers
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Why is my low pass filter decreasing the amplitude when using the inverse DTFT?

Goal: I'm trying to model a waveform in the time-domain for pattern recognition. My plan: Convert signal to frequency domain using FFT Reduce harmonics to hopefully isolate residual data, and make it ...
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How to use numpy covariance result to get a correction factor and make my second signal to exactly overlap on my first signal?

covariance = np.cov(y1_interp, y2_interp)[0][1] print('covariance is', covariance) covariance is 0.00010861874695023591 This number shows how different my signal 2 ...
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1answer
73 views

Which Programming Language Should Be Used for Deep Learning (Deep Neural Network [DNN])?

I will do voice activity detection and speech enhancement based deep neural network. However, I don't know whether to do this via matlab or pyhton. In which programming language can I find more ready-...
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1answer
44 views

Signal values explode when filtering with bandpass and wiener in Python

I have a five second audio (speech with background noise), which I want to process first with bandpass filter and then with wiener filter to reduce noise. Audio is normalized between [-1, 1] and I ...
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1answer
36 views

How to find first local maxima in an unknown dataframe

I get a Dataframe in Python with multiple maxima and minima, I want to find always the first maxima/minima in the frame and ignore the other ones. The problem is that the data has a lot of noise and ...
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1answer
64 views

implementing Prime-factor FFT algorithm

I've been trying for days to implement this algorithm to work with size N samples but I can't manage to do it. my goal is to compute FFT for 100 samples, so I need factor 5 and 2, I wrote a simple FFT ...
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FM and PM waves

I have to find the FM and PM waves corresponding to this sawtooth signal: I have found out the PM wave as: I am getting the FM wave as this : I have plotted this using Python. Can anyone please ...
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1answer
39 views

Evaluate filter matlab function on scipy

I want to reproduce the result given by filter() MATLAB function using scipy.signal functions. The result is not consistent: Matlab example: ...
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1answer
64 views

How to specify parameters in scipy.stft to reproduce published analysis

I am starting a project on this Keggle dataset containing EEG registrations (sampled at 128 Hz) of several subjects. What I am really interested in is the final ...
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27 views

Get Hilbert marginal spectrum with emd package in python

I want to get the Marginal Hilbert Spectrum in Python using the emd package. You can estimate the Marginal Hilbert Spectrum as where, and A(ω,t) is the time-dependent amplitude modulation and ω ...
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1answer
84 views

How to properly band-pass filter an autocorrelated signal?

Let's consider an example ECG time series, sampled at 360Hz: I verified that autocorrelating a signal preserves its frequency content. For instance, both original and autocorrelated data show the ...
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Unexpected results of deconvolution with scipy.deconvolve

Below I have plotted the signal (Lifetime decay) I am trying to deconvolve from a known impulse response function (IRF), as well as the IRF itself. I'm using scipy.signal.deconvolve. Please note for ...
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46 views

How to handle zeros before FFT convolution / deconvolution?

I would like to calculate the input function (unknown) by deconvolution of the output and the "system response" signals. The output is a finite signal from a measure device so it presents ...
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1answer
28 views

Kalman filter for heading estimation with magnetometerv + gyroscope only considers magnetometer

I implemented a Kalman filter to estimate the heading of a robot that is moving in 2D, given the measurements coming from a magnetometer (X, Y) and a gyroscope (Z). The code is the following: ...
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1answer
38 views

If I want to see if a specific period is present in a signal, how do I decide on the number of points we sample the Fast Fourier transform?

I have a time series, which I believe should have daily periodicity, the signal is sampled once every 15 minutes, which means that one period is 288 samples. When I am trying to validate this result ...
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23 views

What input is most appropriate for CFAR processing in FMCW radars and why?

I am estimating range, velocity, angle of arrival from a FMCW radar. To detect potential target candidates points in this 3D domain, I am using a OS-CFAR after the doppler-range to detect the ...
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1answer
200 views

How to calculate the envelope of a complex signal using python [closed]

I used the scipy hilbert function to calculate the envelope of my signal. The problem is that the signal is complex, so it throws an error when I use Hilbert function. I tried to just use the real ...
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1answer
27 views

How to automatically determine if there is NO seasonality from PSD/FFT of time series?

I have around 1000 different time series, and for each one of them I want to automatically determine if there is any seasonality in the time series. Given the assumption that there is seasonality ...
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1answer
224 views

Why Wiener filter is not optimal?

I am investigating Wiener filter in the frequency domain, given by $$ W(\omega) = \frac{S_{ud}(\omega)}{S_{uu}(\omega)}$$ where $S_{xy}(\omega)$ is the cross-power spectral density (CPSD), see scipy....

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