Questions tagged [butterworth]

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How do you convert angular frequency to $\textrm{Hz}$ from MATLAB's $\tt freqz$ function?

Let's say I have used MATLAB's butter function to generate a 3rd order, low-pass, Buttersworth, digital filter. I have a sample rate of $2000\textrm{ samples/second}$, and I want the cutoff frequency ...
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1answer
170 views

Weird results when using MATLAB's $\tt butter$ function?

I'm trying to learn some of the basic MATLAB filter design functions and have been experimenting with the butter function. This function calculates the transfer ...
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1answer
124 views

Order of applying two Butterworth filters (distributivity)

I have a function $f(a, b)$ that applies a linear transformation on a signal $a$, given another signal $b$. I would like to filter the result of $f$ using a 2nd order Butterworth low-pass filter ($\...
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1answer
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Designing Butterworth filter

I'm looking to implement the designing of a Butterworth filter based on the implementation in MATLAB/Scipy into C# but I've ran out of knowledge and can't quite seem how to compute the coefficients <...
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1answer
662 views

Butterworth lowpass filter

In order to understand the behaviour of the butterworth (lowpass) filter I generated a "spectrum" consisting of 1's. I then went to time domain (ifft), applied the ...
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2answers
234 views

MATLAB $\tt butter$ function

I suspect I have a very basic misconception so I'm trying to clarify that here: A signal should be filtered before it is sampled, correct? That is, I always sample an analogue signal at some sampling ...
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2answers
865 views

Butterworth filtering behaving unexpectedly -MATLAB

I'm new to signal processing but I'm trying to understand how the Butterworth filter works. To do so, I did the following: I assumed a sampling frequency of 100Hz and wanted to attentuate everything ...
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1answer
3k views

Butterworth band pass filter

I am trying to build a Butterworth bandpass filter. My intent is to have a pass band between $250\textrm{ Hz}$ and $1000\textrm{ Hz}$. However the plot doesn't look right, as can be seen from the ...
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1answer
884 views

Causal and Non-causal filtering. Strange behavior

I'm trying to understand the behavior of a causal filtering exemplified by figure below. This behavior is making LDA (Linear Discriminant Analysis) misclassify our data, by clearly reverse the signal ...
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1answer
257 views

2D Digital Signal Processing - Applying High Pass on and Image

I have been doing my research on 2D digital signal processing. What I am doing is about noise removal of digital image: Type of noise that I want to remove from an images is like the Gaussian noise ...
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2answers
1k views

Lowpass Butterworth filter design (own poles' calculations)

I'm trying to calculate coefficients for my Butterworth filter of my own. I've found this article that looks really reliable. But I'm trying to implement it in MATLAB and I'm getting bandstop filter. ...
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1answer
2k views

DC component in accelerometer data - filter before or after XYZ Euclidean sum

I'm working on filtering accelerometer XYZ data. The aim is gait-pattern recognition via finding characteristic frequency points and feeding these to a artificial neural network. The trouble is, and ...
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0answers
2k views

Simple (Arduino) digital butterworth filter : why do I see oscillations?

I want to filter deviations from an ADC over time (low pass), not very critical. So I first tried exponential averaging, something like y= (7*y+x)/8. That gave useful results, but there is an obvious ...
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2answers
430 views

Unexpected behaviour when using lfilter with initial filter delay multiple times

I want to filter a very long signal in smaller parts, therefor I am currently using scipys lfilter with an initial filter delay doing multiple iterations of: <...
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1answer
559 views

A few conceptual questions about filter, pole, and bilinear

I am working on a school project on converting a 6th order butterworth high pass filter to digital filter using bilinear transformation. Just got a couple conceptual questions need to be clarified ...
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1answer
527 views

How can resonance be added to a fractional order Butterworth low pass

I am interested in how to add resonance (Q) to the magnitude response of a Butterworth low pass when it is expressed in the form: $$ G^2(\omega)=\frac {1}{1+\left(\frac{\omega}{\omega_c}\right)^{2n}} ...

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