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1answer
22 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
33 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
51 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
votes
1answer
37 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
71 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
54 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
63 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
52 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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1answer
133 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
70 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
votes
1answer
76 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 ...
2
votes
2answers
270 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,...
0
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0answers
67 views

Butterworth high pass filter on image with missing data

My objective is to apply a Butterworth high pass filter on an image with missing data. By default the missing pixels are set to 0. To do so, I compute the FFT of the image, apply the Butterworth high ...
1
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0answers
691 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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0answers
47 views

Determine order of the Butterworth High Pass Filter [duplicate]

I have a coursework to design a high pass butterworth filter with these following parameters: Pass band: 100Hz Gain at pass band: 0.5 Stop band: 50Hz Stop band attenuation: 30dB and my instructor ...
0
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0answers
160 views

Butterworth high-pass filter of order 1, cutoff frequency maximum

I have a flow signal I want to integrate to volume. However, the signal contains a lot of baseline drifting (or low freq. noise), so I need to filter it before I can integrate it. The component in ...
0
votes
1answer
104 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
265 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
2k 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
votes
2answers
449 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
141 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
31 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 ...
0
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0answers
140 views

Envelope frequency in band-pass filter?

I have a respiratory signal that I filter with two different bandpass filters. The signal lies at about 0.2Hz. The first bandpass goes from [0.05,0.7]Hz (left image). I calculate the approximate ...
1
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1answer
36 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
1k 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
475 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
555 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
148 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
39 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
59 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
169 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
293 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
votes
2answers
1k 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
269 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
372 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
873 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
166 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
34 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
690 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
98 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
1k 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 ...
14
votes
6answers
2k 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
511 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
votes
1answer
221 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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3answers
7k 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
vote
1answer
1k 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
votes
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
80 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
65 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 ($\...
0
votes
1answer
996 views

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 <...