Questions tagged [butterworth]
The butterworth tag has no usage guidance.
122
questions
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28 views
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 ...
0
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1answer
36 views
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 ...
4
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2answers
116 views
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 ...
0
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1answer
46 views
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 ...
2
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2answers
105 views
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 ...
12
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3answers
362 views
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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1answer
55 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 ...
2
votes
1answer
112 views
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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1answer
45 views
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 ...
1
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2answers
78 views
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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1answer
51 views
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 ...
0
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2answers
68 views
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 ...
1
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2answers
213 views
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 ...
0
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0answers
109 views
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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1answer
156 views
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 ...
2
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1answer
106 views
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 ...
1
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1answer
162 views
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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0answers
248 views
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 ...
0
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1answer
152 views
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 ...
0
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1answer
37 views
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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1answer
119 views
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 ...
0
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1answer
79 views
Why use both a high pass and a low pass filter in a Butterworth implementation for noise reduction?
I am a new to audio processing . I want to develop an application that reduces audio noise using a Butterworth filter. I found some existing code doing this, but I still do not understand the use of ...
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1answer
97 views
Offset after Butterworth bandpass filtering
guess I'm stuck with this filtering problem and I'm thinking it has something to do with my raw data but I'm not so sure. So the problem is the following, please refer to the figures below, basically, ...
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1answer
76 views
Third octave band zero-phase forwards-backwards Butterworth filter adds amplitude to complex signals?
Overall aim: to take a short signal (likely to be noisy with some tonal components) and filter it into third-octave bands (TOBs), apply frequency-dependent spectral adjustments, then recombine the ...
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1answer
88 views
How to determine the type of a digital filter given its expression?
I'm trying to understand a variant of the filter presented in http://www.stockspotter.com/files/PredictiveIndicators.pdf in the "Code Listing 1.". Its expression is given as follow:
$$y_n = ...
1
vote
3answers
602 views
How to practically correct for group delay imposed by a digital filter (Python)
I'm using Python to filter a signal using a Butterworth filter (scipy.signal.butter) and subsequently passing this through a forward-backward filter with cascaded second order sections (scipy.signal....
1
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1answer
157 views
Ripple in a SciPy Butterworth SOS Filter
I have a script using SciPy for checking the RMS of various Butterworth Bandpass Filters of varying orders.
I would expect the RMS values to increase and decrease linearly and consistently as you get ...
0
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1answer
270 views
Butterworth filter of the acceleration and drifting displacement problem
I am only mechanic engineering and I need to filter my acceleration from MEMS mobile phone which has a noise and drifts. Here is my data. Acceleration vs time from an app mobile phone ...
0
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2answers
291 views
Pre-Warping is not working on bilinear transform
New here and I just wanna ask the question of what happens when your pre warping doesnt work on your bilinear transform?
I am assuming my isnt working as part of my research I have read that the ...
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1answer
194 views
number of multiplications per second required by the system
Consider a system implementing a rational sampling rate change by 5/7: for this, we cascade upsampler by 5, a lowpass filter with cutoff frequency π/7 and a downsampler by 7. The lowpass filter is a ...
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235 views
Number of multiplication operations needed in rational sampling rate change with IIR Butterworth filters
I am trying to get a general sense of how many multiplication operations are needed for a 4th-order Butterworth filter (IIR filter) with a rational sampling rate change. I am excluding any ...
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45 views
Butterworth filter
Can someone please explain how would the image of a biosignal say PPG be affected when a higher-order Butterworth filter is used. Please don't tell about bode curve, I need practical aspects of it.
...
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1answer
142 views
How to figure out number of multiplications in rational sampling
I am trying to understand the following:
Consider a system implementing a rational sampling rate change by $\frac{5}{7}$: for this, we cascade upsampler by 5, a lowpass filter with cutoff frequency $\...
4
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2answers
926 views
Are IIR filters (and specifically Butterworth filter) causal?
I am new to signal processing. I am learning now about filtering and I am trying to implement high pass filter (HPF),and later band-pass filter (BPF). I implement the filters in ...
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1answer
227 views
Roll off rate vs filter order?
The concept of "increasing roll off rate with increasing filter order" applies only to butter worth or also chebyshev and other filter types?
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1answer
89 views
Filtering artefacts and filtering short signals
I have a signal from EEG sensors and I try to denoise it from AC frequencies. For that reason, I estimated PSD of my signal and found that 50 Hz and 100 Hz are likely to represent noise. I constructed ...
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1answer
76 views
How to derive 2nd order Butterworth condition for the damping coefficient mathematically?
The magnitude of 2nd order low pass filter is given as
$$|H(\omega)|^2= \frac{1}{(1-(\frac{\omega}{\omega_o})^2)^2+(\frac{2\zeta\omega}{\omega_o})^2}$$
Now in order to achieve maximally flat within ...
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1answer
111 views
Pole locations of Butterworth filter
I am reading Proakis book "DSP using Matlab", 3rd edition.
I am reading chapter 8, section 8.3, p. 402, and I am confused regarding the equation of poles (roots of denominator of system ...
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2answers
68 views
Design and a notch filter using two Butterworth filters in parallel (MATLAB)
I am doing a project to filter out a 1kHz noise inserted to a 30sec .wav audio file.
To filter out the 1kHz noise, I am required to design using two Butterworth filters connected in parallel where ...
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2answers
130 views
Relationship between order of filter and amplitude/phase response
I am learning about digital filters, for example a lowpass butterworth filter.
In many languages, the implmentation requires specification of the order of the filter, which I believe is the number ...
0
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1answer
97 views
What is absolute ripple specification and how does it arrive in low pass prototype for Butterworth?
Digital Signal Processing by John G. Proakis, Dimitris G. Manolakis(4th Edition) gives the prototype function for Butterworth low pass filter in an analog system which is fine till the point where the ...
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0answers
70 views
Lowpass Butterworth filter equation
I am using a 5th order lowpass Butterworth filter with a varying cutoff frequency, $f_c$, to smoothen some data coming from a spectrometer. An example of a spectrum, plotted with the filtered data, ...
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0answers
164 views
removing noise using Scipy.signal.butter:
I am going to remove the noise from a brain recorded signal. It was a continuous recording and with sample rate=30kHz, it was digitized. So now it is a digital signal.
I have written the code here ...
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4answers
2k views
Butterworth filter transfer function in time domain
Preliminaries
I need to know the response of Butterworth filter in time domain of the following input (at least numerically):
$$
x(t) = \theta(t)(1-\exp\{-at\})\exp\{-bt\}, \quad a,b>0,\quad a\gg b
...
0
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1answer
771 views
How is the formula of the cutoff frequency of a 2nd order Butterworth low-pass filter derived?
According to articles and notes, the cutoff frequency of a 2nd order Butterworth lowpass filter:
is expressed by the formula:
$\omega _c = {1\over\sqrt{R_1R_2C_1C_2}}$
and since $\omega _c = 2 \pi ...
0
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1answer
71 views
Converting a simple analog Butterworth filter into a digital filter
I was just studying an old circuit analysis textbook that was describing how to design a Butterworth filter, and that seemed easy enough.. then, I started to wonder if I can take this analog filter ...
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2answers
173 views
Why is my signal attenuated after applying a HighPass-filter?
I am new to DSP, but I've been attempting apply a butterworth high-pass filter on a 1D array (Values peeking at 300~) to eliminate any noise, yet when applying a high pass filter, I'm ending up with ...
0
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1answer
125 views
Cut-off frequency in Fourier-Spectrum of a noise message
I have a problem involving cut-off frequency.
I have a voice message in an audio file .mat which have an eletromagnetic noise. I am trying to recover the original message by applying digital ...
2
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1answer
601 views
Large spike at beginning of signal after applying Bandpass filter
Foreword: I am a PhD student and fairly unexperienced with many signal processing and engineering concepts, please be gentle.
I am attempting to filter out a frequency range of 1Hz to 2Hz from a 2....
2
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1answer
1k views
Applying a 2D band pass filter (Butterworth ?) to an array with NaNs
I am trying to filter out the low frequencies of an array looking like this :
For now, I am taking transects of this array and applying a 1D - butterworth band pass filter :
...
