Questions tagged [butterworth]
The butterworth tag has no usage guidance.
65
questions
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49 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
54 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
27 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
31 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
64 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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34 views
Filtering frequencies in diferent ranges in Python
I would like to filter frequencies: Alpha, Beta and Gamma. These bands have a relation with the task that I want to classify,
I am using the Gumpy python tool which has a method to apply Butterworth ...
0
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0answers
44 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 (...
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1answer
50 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
60 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
vote
1answer
67 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 ...
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0answers
67 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
74 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 ...
1
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2answers
175 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
votes
2answers
141 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:
...
1
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0answers
181 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
95 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.
...
0
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2answers
656 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
231 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
207 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 ...
3
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2answers
1k 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,...
1
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0answers
1k 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 ...
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1answer
240 views
Butterworth Polynomial from Butterworth Filter
For the butterworth filter, in Matlab command:
[B,A]=butter(2,0.5,'low')
I find this result:
...
0
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1answer
553 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
5k 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 ...
4
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2answers
839 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
256 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
34 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 ...
1
vote
1answer
46 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, ...
1
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0answers
3k 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
716 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 ...
1
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1answer
2k views
why butterworth bandpass filter changes signal in the passband?
I want to apply a butterworth bandpass filter to EEG signals and it's not working so I tried with a simple signal:
t=[0:0.01:10];
s3= 9*sin(2*pi*4*t);
Still ...
1
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1answer
191 views
Butterworth high pass filter
My signal's base line is around 1. When I apply Butterworth high pass filter with cut off frequency Fc = 2Hz signal's base line drops to 0. My data are from the accelerometer. Is this behavior normal ?...
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1answer
42 views
Confusion regarding a library of Digital Signal Controller
I'll be using a NXP DSC with 56800Ex core and my aim is to implement a Elliptic IIR Filter in it.
The User Reference Manual of the 'General Digital Filters Library' (which is available here) has ...
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0answers
64 views
Difference between MATLAB's $\tt butter$ and my calculated coefficient
So I figured recently that MATLAB's butter function was giving slightly different coefficients than those I calculate for a simple first order low pass filter, and ...
0
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1answer
203 views
Parameters of Butterworth filter that approximates the amplitude response of a Gaussian filter?
For a given narrowband Gaussian filter with a specific central frequency and filter width, I need corners of a bandpass Butterworth filter whose amplitude response is close enough to the Gaussian ...
0
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1answer
426 views
Different phase response plots using MATLAB's $\tt freqz$ and $\tt fvtool$?
I have a butterworth filter in MATLAB:
[B, A] = butter( 2, 3000/16000*2, 'high' );
I plot it in two ways:
using freqz:[h,w]...
2
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2answers
2k views
How to plot magnitude and phase response of 2 cascaded filters in Matlab?
How would I go about plotting a magnitude and phase response of a system that consists of two cascaded 2nd order Butterworth filters in Matlab? Filters are the same.
...
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1answer
372 views
2-way crossover by using MATLAB's $\tt butter()$ and $\tt filter()$
I am trying to do a 2-way crossover audio filter in MATLAB in two ways:
using crossoverFilter() from Audio System Toolbox
using standard MATLAB functions ...
2
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1answer
464 views
4th order high-pass filter on a DSP: standard or biquads?
I have two C implementations of 4th order high-pass filter (fs = 16 kHz, cut-off=100 Hz, designed using Matlab ...
0
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1answer
1k views
If a filter has a non-linear phase lag will the output signal be distorted?
EDIT: From here (https://www.mathworks.com/help/signal/ref/butter.html)
it appears that an Butterworth filter has a non-linear phase lag at the normalized frequency of 0.5 onwards.
Does that mean that ...
2
votes
1answer
231 views
Can't make sense from VHDL butterworth filter implementation
I am trying to understand the VHDL implementation of the 3rd order Butterworth filter published on opencores. Supposedly the filter implementation gets away with only division and multiplications by 2 ...
0
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1answer
39 views
While converting discrete filter specs into continuous filter specs, why do we multiply gain by T
As I know so far that when we trying to design a DF(discrete filter) with specific specs "in terms of $\omega$", we take these specs and map it into continuous domain $H(j\Omega)$ using a certain ...
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1answer
979 views
Calculating cutoff frequency for Butterworth filter
I have a problem while calculating cutoff frequency, suppose we have these specs.
Firstly, I calculated the order of the filter and got $N=5.8858$ and round it up to get $N=6$.
Now I'm supposed to ...
0
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1answer
116 views
Design of butterworth filter
I was trying to design a butterworth filter of arbitrary order. Then i came across this presentation:
Lecture 9: Poles, Zeros & Filters, by Peter Cheung, Imperial College London
I understand ...
1
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1answer
2k views
What is the significance of Butterworth filter in image processing?
Filters like mean,median,gaussian,bilateral and adaptive forms of these filters are used commonly in image processing but not Butterworth filter.
The reasons I could think of are
a) Butterworth ...
15
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6answers
3k views
Filter design by distributing poles and zeros on parametric curves
An $N$th order Butterworth low-pass filter of cutoff frequency $\omega_c$ can be designed by distributing $N$ poles uniformly with respect to parameter $0 < \alpha <1$ on an s-plane parametric ...
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1answer
730 views
Phase shift in higher order filters
I was doing some research on filters, So I designed butterworth filter based on pole locations. I applied to a simple sine signal to check for the outputs. I cannot find the reason for what I noticed.
...
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1answer
263 views
Designing butterworth filter with pole placement
I am trying to design a Nth order continous time Butterworth filter in state space, with pole placement technique.
...
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4answers
11k views
Higher-order (Butterworth) filters
This is a general question, I am just trying to understand the concept. Why should we use higher-order filters, other than a 1st order (of any type for that matter, but we can keep the discussion to ...
1
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1answer
2k views
Butterworth filter approximation: derivation and output poles
I am having trouble understanding the exact derivation of the butterworth filter and how it results in the output of the poles. I have researched multiple lecture series and textbooks and this is my ...
