Questions tagged [butterworth]
The butterworth tag has no usage guidance.
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Getting displacement from the accelerometer data for vertical motion
I have an accelerometer sensor with gyro and need to figure out the vertical displacement from the acceleration data. The device that contains the accelerometer will move up and down in fairly ...
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Several Low pass filters generate offset when applied on an embedded system on C++
I need to implement a real time butterworth low pass filter on some data, I have an already implemented and tested butterworth function, but when filtering data from one specific variable I get an ...
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Denoising Signal With Butterworth-Filter
im trying to denoise a signal to which i added AWGN. Here is what ive done so far:
...
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IIR bandpass filter attenuates frequencies within the pass band
I applied Butterworth filters (order=5) that have different cutoff frequencies to a simple signal composed of four sinusoidal oscillations and computed its PSD.
<...
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132
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Calculating the filter coefficients for 2nd order bandpass and bandstop Butterworth filter
I want to calculate the filter coefficients for both bandpass and bandstop filter for 2nd order Butterworth filter, like
...
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197
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How to implement a 3rd order Butterworth IIR allpass filter with perfectly flat frequency response?
I'm working on an audio plugin which splits audio into frequency bands for individual processing. The filters must have zero latency, so no linear phase filters.
I would like to have perfect ...
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How to obtain filtered impulse response from frequency response?
I am trying to find the reverberation time of a room using the Schroeder method (i.e., Reverse-time integration method). Therefore, impulse responses should be measured first.
There are many ways to ...
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Why do we have a negative gain after a certain point in frequency domain for a channel filter?
Why do we have a negative gain(i.e. not negative as in polarity but gain < 1) after a certain point (1500 Hz). What is the reason and purpose for this. Why is that point the same for both DC and AC ...
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Why odd-order Butterworth filters don't behave the same as even-order in crossovers?
I have noticed that when you create a crossover using even-order Butterworth filters, you need to use two filters instead of one (Linkwitz-Riley) in order to obtain a flat amplitude response (two low-...
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filtering EEG data with scipy.signal
I have EEG data recorded with a sampling rate of 256 Hz. Each recording contains 19 EEG channels. Other channels (like ECG data) are ignored. The recordings of 10 patients are 20 minutes long each, ...
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How to implement the discrete Butterworth
I'm trying to implement the Butterworth filter as a high pass filter inside a function, where every time stip a measurement will be passed (inside this function I do have buffers for storing the data)....
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Sampling frequency in bilinear transform when designing butterworth filter
I'm trying to design digital Butterworth filter from scratch. First I use butterap to design an analog prototype to get zeros, poles and gain
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How to design digital Butterworth filter and return its zeros, poles and gain
I'm implementing digital Butterworth filter and encounter some numerical problem when filter order is high using direct form, so I wonder how to design the digital Butterworth filter and return its ...
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Butterworth Filter at high Frequencies
So I have this signal sampled at 300 Hz to begin with and this is the frequency domain:
I apply a second order butterworth filter using scipy with a cutoff frequency of 12.6 Hz and this is the ...
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Signal processing in Python vs C++ (band-pass filter)
I have implemented Python signal processing code using a butter bandpass filter and order 3. It is working pretty well.
I am required to implement the same signal ...
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Why don't unit circle poles lead to infinite amplitude response for Butterworth lowpass?
This is probably a very stupid question. In many places (e.g. here), the Butterworth filters, e.g. lowpass, are described as being "allpole" filters, that have all of these poles on the unit ...
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Lowpass Filter for Lock-In-Amplifier
I am implementing a Lock-In-Amplifier in Python with scipy for measurements with light with a decimation afterwards. Right now, this is implemented with an average. This works fine, but I am trying to ...
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Butterworth filter cutoff attenuation is not exactly 0.707(-3dB)
The documentation of scipy Butterworth filter says its cutoff attenuation is 0.707(-3dB). To validate this, I created a square wave signal, performed FFT and implemented a bandpass filter with a band ...
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Formula to compute FIR and IIR Filter coefficients
I am trying to understand filter design. I am trying to implement butterworth filter which would have high,low and bandpass using the difference equation representation for FIR and IIR. Given the low ...
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Accounting for phase shift in time-dependent signals
Background:
I am using a vibration sensor and arduino to record signals and log them with timestamps, where the signals need to be time accurate so that I can glean information about which frequencies ...
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212
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Performing STFT after Butterworth Filter Seems Lower in Resolution
I have a signal recorded at 2MHz sampling rate. Before any decimation might be required, I first looked for peaks in my periodic recorded signal using STFT/spectrogram. From here, I can clearly see ...
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Questionable results of on-line butterworth bandpass filtering using scipy.signal.lfilter
I have a data_stream that I'm attempting to filter using two on-line butterworth bandpass filters to extract two frequency bands of interest. The original ...
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Sampling frequency vs Signal frequency
I've started recently working with the ADXL345 accelerometer with the goal of finding the velocity.
And so far, I'm getting "okay" results after applying a second-order Butterworth filter to ...
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146
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I do not understand the frequency calculation used in the construction of this IIR digital Butterworth Low pass filter using MATLAB
The question is to design a Low Pass Butterworth IIR Digital filter. The following code below has
the specifications with $A_p$ being the passband attenuation, $A_s$ the stop band attenuation, $f_{pb}$...
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How can I reverse engineer the parameters of this butterworth filter?
I am trying to develop an application which will need a bandpass filter. The sampling rate is 30Hz, and the frequency range I'd like the filter to preserve is: 0.5Hz-4Hz.
I've used mkfilter to ...
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925
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How to apply Butterworth high pass filter in the frequency domain?
I have a time series of measurements which I want to high pass with Butterworth filter.
Python scipy package has a built in function for Butterworth filter (signal.butter) and I know how to apply it ...
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I can't hear my sound after filtering
I am studying on a project which my supervisor gave me this semester. It has multiple steps. Basically, I have my own audio. I added AWGN to this sound using awgn() ...
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548
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SOS-matrices' order does not correspond to given parameter when designing bandpass with scipy.signal.butter
I do not understand why this scipy operation:
...
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25
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How to deal with [h] coefficients which are 0 from sos-matrix
Calling scipy.signal.sosfreqz with a sos-matrix describing an ordinary butterworth bandpass returns an array of h coefficients, ...
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215
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Theory behind the matlab butter function with the parameters n and [Wl, Wh]
I am writing the theoretical background in my thesis but my thesis is more centered on deep learning and the signals that I am using for classification were filtered through the ...
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265
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BPF Filtering with DSP IIR Realtime C++ filter library
I am working with complex samples, I have a main signal at 630KHz, my Fs is 1.26MHz and BW is 12.6KHz.
If I plot a frequency-magntitude spectrum it looks like this:
As you can see along with my main ...
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Implementing a Butterworth Filter Manually in C/C++ via Second Order Sections
Short background: I want to implement a lowpass butterworth filter in C/C++. The end goal is to use this in a low-latency Python program, for which of course ...
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What is the warm-up period of a Butterworth filter?
I am not sure if I use the correct term which may be the reason why I was not able to find the answer, but what I mean by the warm-up period is the number of samples required for the filter to produce ...
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Butterworth filter poles
Hi,
I'm looking at this textbook question and trying to get a better idea of exactly what its asking.
For the processing to be real valued each pole would have to have a complex conjugate right?
So ...
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Mapping of Classic Filters for Digital Filter Design
Of the four classic analog filter types: Butterworth, Chebyshev, Elliptic and Bessel- are any of these relegated to obsolescence for purposes of digital filter design in comparison to optimized ...
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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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Butterworth Filter Transfer Function
Butterworth Filter frequency response is given as:
$$H_a(j\Omega)=\frac{1}{\sqrt{{1+\left(\frac{\Omega}{\Omega_c}\right)^{2N}}}}\quad \text{where $N$ is the order of the filter}$$
and for the transfer ...
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Paper replication: Validating the proper way to pass .wav audio breathing data through a bandpass filter
I am working on trying to apply a low and high pass filter to an audio file that contains a set of exhalations over a microphone. The inhalations have been cut out of the file, and the exhalations are ...
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What is the $Q$ of successive Second-Order Sections of an $N$th-order Butterworth low-pass filter?
What if you had an $N$th-order Butterworth lowpass filter filter with -3 dB frequency of $\Omega_0$?
$$ \Big| H(j\Omega) \Big|^2 = \frac{1}{1 + \left(\frac{\Omega}{\Omega_0}\right)^{2N}} $$
The number ...
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153
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narrow band filtering of a signal that is sampled at high frequency
I have a signal that is sampled at 2KHz. The frequency band of interest is from 1/60 Hz to 1 Hz, and I want the final signal to be downsampled to 10 Hz.
What is the best way to do this?
I read that ...
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Butterworth filter higher order
I am new (very beginner) to signal processing and I am trying to understand how the Butterworth filter operates.
According to my current understanding of filters, there seems to be a tradeoff between ...
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Transfer functions for Scipy and Matlab's Butterworth filter don't seem to match theory
The squared transfer function for a Butterworth filter of order $n$ should be
$$
|H(f)|^2 = \frac{1}{1+\left(\frac{f}{f_c}\right)^{2n}}
$$
where $f_c$ is the cut-off frequency. (Here's one of many ...
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Filter 3D volumetric image with a Butterworth filter in Python
I have been looking for a way to filter a 3D volumetric image in python with a Butterworth filter, but I haven't found any good solution.
I have tried this:
...
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why does butterworth IIR filter for a square pulse show ripple on edges in time domain but not the same for sine wave
I am using butterworth filter for both square pulse and sine wave. In case of square pulse, butterworth produces some sharp ripple of edges of square pulse in time domain for varying butterworth order ...
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Difference between MATLAB zp2sos and python zpk2sos functions
I am trying to port some code from MATLAB to python. The goal is to use Butterworth filter (4th order, bandpass) API and convert it to second-order sections. I get the same output between MATLAB and ...
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LPF in the stage of IQ demodulator is it a analgor filter or digital filter?
I recently designed the LPF of the IQ demodulator using the Butterworth LPF refering to https://dspillustrations.com/pages/posts/misc/baseband-up-and-downconversion-and-iq-modulation.html. But I have ...
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Pre-Processing Wi-Fi Channel State Information (CSI) Data
I was successfully able to collect some CSI data using the existing tool(s) on GitHub (https://github.com/StevenMHernandez/ESP32-CSI-Tool). The CSI data is a pair of imaginary and real number which ...
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Creating a 4th order Butterworth filter R
I have sampled my data at 2000 Hz and want to generate a fourth order low-pass zero-lag filter with a cut-off frequency of 150 Hz.
I have put the code below that I have created but I have the ...
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I am looking for an analytic description of a continuous-time Butteworth High-pass filter in the time domain (=impulse response)
having derived the Butterworth Lowpass Time domain response, I am now struggling to find a similar function for a Butterworth Highpass filter. I understand you need to replace s by 1/s. But this leads ...
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Butterworth filter's gain formula does not agree with R's `signal` package
I'm trying to calculate the Butterworth filter gain. If I use the formula mentioned on Wikipedia:
$$
G^2(\omega) = \frac{G_0^2}
{1+\left(\frac{j\omega}{j\omega_c}\right)^{2n}}
$$
I don't get a ...
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