Questions tagged [butterworth]
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85
questions
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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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43 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
27 views
Difference in results between iirj and mkfilter with Butterworth filter in BandPass
When I generate a filter on www-users.cs.york.ac.uk/~fisher/mkfilter/trad.html
and another iirj (github.com/berndporr/iirj) these are not the same results.
Configuration (mkfilter):
Type : ...
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0answers
25 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 ...
1
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3answers
383 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 ...
0
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1answer
47 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
30 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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20 views
Apply a butterworth filter to columns of a large dataframe
I have a large dataframe (7200, 132) and each column is a signal. I want to apply a butterworth filter to each signal, however, I'm not sure how to do this in Python.
When I do it in matlab I can ...
2
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2answers
86 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
32 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
91 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....
1
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1answer
35 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 :
...
1
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1answer
65 views
Plotting curved peaks on PSD graph
I am a PhD student with little engineering experience, currently attempting to recreate the signal processing techniques used in this paper: Monitoring Vital Signs and Postures During Sleep Using WiFi ...
0
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0answers
36 views
First Order Butterworth filter has low frequency noise and only cuts off about 13db/decade
I designed a low pass Butterworth filter like so
...
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1answer
58 views
Frequency response plot and actual behavior of a digital Butterworth LPF
I have been struggling with a not-too-high (2nd) order digital Butterworth low-pass filter both in SciPy and MatLab (latest of both).
The intention is to apply this filter on signals with different ...
0
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1answer
108 views
Using a Butterworth high-pass filter together with Fast Fourier transform
I have a signal and I'm interested in identifying the dominant frequencies greater than 1/3600 Hz. To do this, I use Fast Fourier Transforms and examine the locations of the peaks in the frequency ...
1
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2answers
127 views
How Butterworth low-pass filter can be applied on a digital signal (i.e. discrete representation of a signal)?
I would like to know how to apply a low pass filter (Butterworth) to a digital signal. So, I have some values of the signal, let's say $S(t)$. Those values are equally spaced in time. I have read the ...
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1answer
86 views
what is the theory behind Butter function?
I want to understand why this code used tan and cos ?
...
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0answers
18 views
What is the meaning of these Fixed Point Properties e.g.CustomSectionInputDataType?
I was trying tom implement a Butterworth filter and i came across a example on Mathworks site which emphasizes to customize various terms related to the filter.
Following are some of the terms i could ...
0
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1answer
393 views
How to choose order and cut-off frequency for low-pass Butterworth filter?
When using IMU data (accelerations and angular velocities), many papers use a 4th order low-pass butterworth filter with a cutoff frequency of 5 Hz. However, none of them really justify why those ...
0
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1answer
66 views
Why does sampling frequency affect the filter results?
I have a big issue, basically my goal is to create a low-pass butterworth filter around 0-35Hz with a sampling frequency of 5000Hz.
My Matlab code is
...
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0answers
280 views
Butterworth cutoff frequency normalization
The issue: I am trying to reproduce the step detection technique as described in this paper. You can see the proposed step detection in the image below. The first part of this technique is to use a ...
0
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1answer
88 views
Bandpass filter with very high sampling rate
Consider a bandpass filter with Low Cut 17Hz, High Cut 22 Hz, Fs = 45000 Hz and Order = 6. When I pass a mixture of multiple sinusoidal waves through this filter (with a sine wave of frequency 20 Hz), ...
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0answers
34 views
Correctly interpret Butterworth filter frequencies
I am using the butter function from the signal package in R to filter my data.
The data is Fourier-transformed (complex numbers) - and I want to filter out specific frequencies (I have a 256Hz ...
0
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1answer
75 views
Analytical design of a bandstop Butterworth filter
I am trying to analytically design a bandstop Butterworth filter. I am trying to use:
$$|H(s)|^2 = \frac{1}{1+\big(\frac{s}{j\omega_1}\big)^{2N}}+\frac{1}{1+\big(\frac{s}{j\omega_2}\big)^{-2N}}$$
to ...
2
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1answer
166 views
Odd-order Butterworth filter gain at cutoff frequency
Wikipedia gives the gain of an n-order Butterworth filter as
$$G^2(\omega)=\left |H(j\omega)\right|^2 = \frac {{G_0}^2}{1+\left(\frac{j\omega}{\omega_c}\right)^{2n}}$$
here. If you look at the gain ...
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0answers
72 views
how to detrend a carrier phase with butterworth filter?
I am new with detrending techniques, I have a carrier phase measurements and I want to detrend it by 6th order butterworth digital filter. After creating the digital filter I get its numerator (...
0
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1answer
73 views
difference between conventional analog butterworth filter and that implemented through IIR
I am confused what is difference between conventional analog butterworth filter and that implemented through digital technique using IIR
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1answer
115 views
“Side Lobes” When Using a Butterworth filter
So I am attempting to filter a signal containing frequencies at 7Hz, 11Hz, and 74Hz. The signal lasts for 30s and looks like this between -1s and 1s:
Using a butterworth filter of order 2 with lowcut=...
1
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1answer
85 views
iir biquad filter not working
I am trying to implement a butterworth bandpass filter
My filter requirement is Fs= 500Hz, Fc1=0.4Hz, Fc2=4Hz, Oreder=2.
Below is the code which is implemented on 16bit-mcu and is called for every ...
1
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0answers
90 views
Digital or analogue filtering?
I'm trying to self learn the art of signal processing whilst moving through my third year pure maths degree.
Sorry if my terminology is incorrect however I hope I am understandable!
I am looking at ...
0
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1answer
115 views
Time-domain LPF not showing expected behavior
I am trying to implement a simple first-order Butterworth Low-Pass filter in Python. I have some code that makes use of scipy.signal.butter and scipy.signal.filtfilt. It works fine, but I wanted to ...
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2answers
348 views
How to compare many bandpass filters (for their signal propogation delay)?
Let's say we have an audio signal sampled at 96 kHz, and we want to compare several bandpass filters to find the one with the lowest rectangular-envelope-propagation-delay (see graph below).
The band ...
2
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2answers
267 views
Initialize Hi Pass Filter
I want to remove the DC from a ADC, so I designed a two-pole, 1 Hz high-pass Butterworth filter for a signal sampled at 10kHz. The filter coefficients are:
...
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0answers
247 views
How can I manually find the coefficients, poles and zeros of Butterworth low pass filter in MATLAB instead of using the built-in functions?
Actually I need to filter a raw ECG signal using low pass Butterworth filter at 70 hertz. And j need to implement the Butterworth filter first for that. Please any help since I'm very new to this ...
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1answer
246 views
Question of Digital filter; stability and order
Below 1~6 are my question.
Shortcomings of IIR filter.
Mean of unstable. (Things that will happen when system is unstable.)
How to select the best order(n).
What happens when I raise order too much.
...
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2answers
1k views
Bandpass butterworth filter in python is not working
I've implemented this bandpass filter in matlab for the audio signals and it's working as expected. Now, I tried to implement the same thing in Python but it doesn't produced expected results, it just ...
0
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1answer
448 views
How to decompose raw acceleration signals into gravity and dynamic acceleration?
I have a data from $3$-axis $50$ Hz accelerometer, acceleration over each of $3$-axis: $acc_X,\ acc_y,\ acc_z$.
I want to decompose acceleration into gravity and movement components.
First ...
0
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1answer
356 views
4th order butterworth filter using frequency response formula
I know this may be a kind of basic question, but I have my head wrapped over it for some time and hadn't found a solution.
I want to generate the frequency response of a 4th order butterworth filter ...
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2answers
2k views
How to implement a filter associated to a specific wavelet
I am working on ECG signals, to eventually extract features in order to detect an arrhythmia and classify it.
I am using Discrete Wavelet Transform with biorthogonal wavelet bior6.8
During my research,...
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0answers
2k views
Implement a Butterworth Filter in C#
I'm very new to signal processing, but was asked to implement a filter function for Butterworth low pass filter for given order, cutoff frequency and sample rate.
After reading some articles I think ...
0
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1answer
397 views
Butterworth Polynomial from Butterworth Filter
For the butterworth filter, in Matlab command:
[B,A]=butter(2,0.5,'low')
I find this result:
...
1
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1answer
1k views
Why is the second-order-section cascade approach giving “worse” results?
It seems that as a general rule, for digital IIR filters of order more than 2, one is encouraged to use a cascade of second order sections, for reasons connected to the poor stability of high-order ...
3
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1answer
8k views
Apply butterworth filter (lowpass) to a signal
I'm working on a DSP lab and I can't figure out how to apply the filter I've created to a sound. The only thing I found online that did something to my sound was ...
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2answers
1k views
What is the largest “safe” order for the digital Butterworth filter of a given signal?
Say I want to apply a zero-phase Butterworth bandpass filter, implemented in MATLAB using butter and filtfilt. So, for an order-$...
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1answer
400 views
Butterworth low pass filter zeros location after bilinear transformation explanation
I am studying in a text book the transformation of a continuous time Butterworth low pass filter into a discrete time filter by means of bilinear transformation:
$$
s = \frac{2}{T_d}*\frac{1-z^{-1}...
0
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1answer
37 views
Incorrect Butterworth filter outcome using Rational Transfer Funcion
I've been playing with Second-Order Butterworth high-pass filter for a while.
I've calculated the coefficients using Matlab function and I wanted to use them to filter simple sine wave generated by ...
2
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1answer
50 views
Audio signal series' beginning points(about 50) distort after a bandpass filter
I am using some bandpass filters to detect a certain freq of the sampled audio series in noisy environment. Everything is OK except this:
I found that for many bandpass filters I tried(butterworth, ...
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0answers
4k views
Design of a Butterworth lowpass filter in MATLAB
I'm using the Signal Processing Toolbox in MATLAB to design a Butterworth low-pass filter. I'm told that my filter has been giving some unexpected results. In particular, when the values from this ...
0
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1answer
995 views
Whats is the difference between FIR/IIR filters and Chebyshev/Butterworth filters
I am new to Signal Processing. From my understanding -- FIR/IIR just refer to the placement of poles and zeros in the z-domain helping us achieve convolution, if FIR and ??? in IIR.
Chebyshev and ...
