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Questions tagged [butterworth]

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0
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1answer
20 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
votes
1answer
44 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 ...
0
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0answers
16 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
40 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
37 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
-1
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1answer
44 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
62 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
54 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
52 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
vote
2answers
153 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
103 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
158 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 ...
0
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1answer
83 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
votes
2answers
518 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
votes
1answer
200 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
184 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
votes
2answers
982 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 ...
0
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1answer
211 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
votes
1answer
491 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 ...
4
votes
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 ...
5
votes
2answers
769 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-$...
1
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1answer
234 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
42 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
votes
1answer
698 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
1k 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
vote
1answer
183 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 ?...
0
votes
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 ...
0
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0answers
62 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
votes
1answer
197 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
votes
1answer
410 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. ...
-1
votes
1answer
361 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
votes
1answer
448 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
votes
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 ...
1
vote
1answer
217 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
votes
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 ...
1
vote
1answer
958 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
votes
1answer
115 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 ...
16
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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 ...
1
vote
1answer
684 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. ...
0
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1answer
258 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. ...
0
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4answers
10k 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 ...
0
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1answer
2k views

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 ...
0
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1answer
98 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 ...
2
votes
1answer
71 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 ($\...