Questions tagged [butterworth]
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102
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Hello, i wish to construct a working 4th order active low pass Butterworth filter circuit with tunable cut-off frequency, can anyone help
I have found 4th order low pass butterworth filter but i have no idea how to produce tunable cut-off frequency. it is for a college project
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18 views
Third octave band zero-phase forwards-backwards Butterworth filter adds amplitude to complex signals?
Overall aim: to take a short signal (likely to be noisy with some tonal components) and filter it into third-octave bands (TOBs), apply frequency-dependent spectral adjustments, then recombine the ...
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1answer
64 views
How to determine the type of a digital filter given its expression?
I'm trying to understand a variant of the filter presented in http://www.stockspotter.com/files/PredictiveIndicators.pdf in the "Code Listing 1.". Its expression is given as follow:
$$y_n = ...
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3answers
66 views
How to practically correct for group delay imposed by a digital filter (Python)
I'm using Python to filter a signal using a Butterworth filter (scipy.signal.butter) and subsequently passing this through a forward-backward filter with cascaded second order sections (scipy.signal....
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1answer
51 views
Ripple in a SciPy Butterworth SOS Filter
I have a script using SciPy for checking the RMS of various Butterworth Bandpass Filters of varying orders.
I would expect the RMS values to increase and decrease linearly and consistently as you get ...
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1answer
102 views
Butterworth filter of the acceleration and drifting displacement problem
I am only mechanic engineering and I need to filter my acceleration from MEMS mobile phone which has a noise and drifts. Here is my data. Acceleration vs time from an app mobile phone ...
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2answers
91 views
Pre-Warping is not working on bilinear transform
New here and I just wanna ask the question of what happens when your pre warping doesnt work on your bilinear transform?
I am assuming my isnt working as part of my research I have read that the ...
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1answer
109 views
number of multiplications per second required by the system
Consider a system implementing a rational sampling rate change by 5/7: for this, we cascade upsampler by 5, a lowpass filter with cutoff frequency Ļ/7 and a downsampler by 7. The lowpass filter is a ...
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90 views
Number of multiplication operations needed in rational sampling rate change with IIR Butterworth filters
I am trying to get a general sense of how many multiplication operations are needed for a 4th-order Butterworth filter (IIR filter) with a rational sampling rate change. I am excluding any ...
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37 views
Butterworth filter
Can someone please explain how would the image of a biosignal say PPG be affected when a higher-order Butterworth filter is used. Please don't tell about bode curve, I need practical aspects of it.
...
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1answer
68 views
How to figure out number of multiplications in rational sampling
I am trying to understand the following:
Consider a system implementing a rational sampling rate change by $\frac{5}{7}$: for this, we cascade upsampler by 5, a lowpass filter with cutoff frequency $\...
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2answers
380 views
Are IIR filters (and specifically Butterworth filter) causal?
I am new to signal processing. I am learning now about filtering and I am trying to implement high pass filter (HPF),and later band-pass filter (BPF). I implement the filters in ...
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1answer
71 views
Roll off rate vs filter order?
The concept of "increasing roll off rate with increasing filter order" applies only to butter worth or also chebyshev and other filter types?
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1answer
39 views
Filtering artefacts and filtering short signals
I have a signal from EEG sensors and I try to denoise it from AC frequencies. For that reason, I estimated PSD of my signal and found that 50 Hz and 100 Hz are likely to represent noise. I constructed ...
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1answer
44 views
How to derive 2nd order Butterworth condition for the damping coefficient mathematically?
The magnitude of 2nd order low pass filter is given as
$$|H(\omega)|^2= \frac{1}{(1-(\frac{\omega}{\omega_o})^2)^2+(\frac{2\zeta\omega}{\omega_o})^2}$$
Now in order to achieve maximally flat within ...
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1answer
70 views
Pole locations of Butterworth filter
I am reading Proakis book "DSP using Matlab", 3rd edition.
I am reading chapter 8, section 8.3, p. 402, and I am confused regarding the equation of poles (roots of denominator of system ...
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2answers
33 views
Design and a notch filter using two Butterworth filters in parallel (MATLAB)
I am doing a project to filter out a 1kHz noise inserted to a 30sec .wav audio file.
To filter out the 1kHz noise, I am required to design using two Butterworth filters connected in parallel where ...
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2answers
53 views
Relationship between order of filter and amplitude/phase response
I am learning about digital filters, for example a lowpass butterworth filter.
In many languages, the implmentation requires specification of the order of the filter, which I believe is the number ...
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1answer
42 views
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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52 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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54 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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84 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 ...
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3answers
919 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 b
...
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1answer
356 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 ...
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1answer
43 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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102 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 ...
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2answers
112 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 ...
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1answer
57 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 ...
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1answer
276 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....
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1answer
372 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 :
...
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1answer
94 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 ...
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1answer
66 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 ...
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1answer
168 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 ...
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2answers
279 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
107 views
what is the theory behind Butter function?
I want to understand why this code used tan and cos ?
...
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19 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 ...
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1answer
1k 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 ...
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1answer
147 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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1answer
100 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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80 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 ...
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1answer
216 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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100 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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2answers
3k views
FIR butterworth also possible or just IIR?
can we use butterworth and other such filters like chebyshev,elliptic etc with FIR
or they can be only used with IIR?
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1answer
76 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
142 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=...
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1answer
92 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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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 ...
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1answer
131 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
434 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 ...
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2answers
355 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:
...
