## Forums Search for: Butterworth

## equations for Butterworth IIR filters, where are they hiding?

inI came across this webpage: http://mymbs.mobeard.org/~pfisher/fov2-0010016c/fov2-0010016e/FOV2-001001A3/chapters/25katsianos /index.html It...

I came across this webpage: http://mymbs.mobeard.org/~pfisher/fov2-0010016c/fov2-0010016e/FOV2-001001A3/chapters/25katsianos /index.html It lists the equations for the filter coefficients up to 5th order in a form that seems relatively easy to implement. I have come across other derivations that seem more laborious. Now unfortunately, the author has made the equations as GIFs with very small

## Small/easy Challenge

inWorking on some other problem the below coefficient expressions popped out as a byproduct. I'm curious to know if the expressions are (well)...

Working on some other problem the below coefficient expressions popped out as a byproduct. I'm curious to know if the expressions are (well) known. Hopefully you don't find it too lame that I post it as a challenge to derive the expressions. I have no idea how easy it is. A 3rd order Butterworth lowpass filter, H(z), can be realized as a parallel connection of two allpass filters, one of order ...

## Fixed point implementation of 4'th order IIR filters

inHi Does anyone have some guidelines on how to implement a 4'th order low-pass Butterworth IIR filter in fixed point. My cut-off frequency is...

Hi Does anyone have some guidelines on how to implement a 4'th order low-pass Butterworth IIR filter in fixed point. My cut-off frequency is relatively close to the DC frequency so high precision is needed for the coefficients. What about realization structure and so on! I have implemented the bit-flipping algorithm in http://www.cmsa.wmin.ac.uk/~artur/pdf/Paper16.pdf for quantization of...

## matlab filter shape versus sample frequency

inHi. I was using some matlab functions to show the shapes of some basic butterworth filters when I noticed that my shapes were changing depending...

Hi. I was using some matlab functions to show the shapes of some basic butterworth filters when I noticed that my shapes were changing depending on my sampling frequency. Of course, I wouldn't expect this. Can anyone explain why this is happening? Thanks, Blair I have pasted code here which best demonstrates what I mean... % Written by: Blair Fonville % Last Modified: Jan 12...

## Re: Bessel Filter (Digital)

in> could we be more clear as to why Bessel seems okay for analog and not > with digital? > > i have never implemented a Bessel filter in either...

> could we be more clear as to why Bessel seems okay for analog and not > with digital? > > i have never implemented a Bessel filter in either domain, i don't > remember even doing it in school. i do remember seeing it and the > design equations and such in sections besides that of other filters > (Butterworth, Tchebyshev 1 and 2, Elliptical, Gaussian). i remember > seeing plots of their group d

## Which noise?

inDear chaps, I have a problem. I have a signal recorded from a ultrasonic transducer of a chemical reaction. It is rich of noise, expecially...

Dear chaps, I have a problem. I have a signal recorded from a ultrasonic transducer of a chemical reaction. It is rich of noise, expecially the white one. I tried to filter with normal filter (butterworth band pass), but I did not obtained a lot of success. So, I thought was better delete the White gaussian noise with an adaptive filter. I used the demo of Simuling of LMS but I have probl...

## DSP sample rate question

inHello, I have a quick question. Say I am working on a DSP low pass filter that will be utilizing a 10Hz cutoff frequency. This is a two pole...

Hello, I have a quick question. Say I am working on a DSP low pass filter that will be utilizing a 10Hz cutoff frequency. This is a two pole butterworth based recursive (IIR) filter. I -think- our highest frequency component will most likely be (rate of change in digital input to the IIR) around 8kHz. My manager who is primarily experienced in analog filter thinks that we'll only need to w...

## Simulating higher order IIR filters using cascaded low order sections

inI'm trying to make a tool that implements various types of IIR filters up to a certain maximum filter order (8 in my case). I've been learning...

I'm trying to make a tool that implements various types of IIR filters up to a certain maximum filter order (8 in my case). I've been learning about the bilinear transform and how to use it to turn an analog transfer function into a something that can be implemented as a digital filter. I already have working implementations for 1-5th order butterworth low pass filters, but I've not

## What is wrong in this IIR filter code?

inHi, Given are following coefficients to a second order butterworth highpass filter with a 3 dB cutoff freq of 4.48 Hz: double a0 =...

Hi, Given are following coefficients to a second order butterworth highpass filter with a 3 dB cutoff freq of 4.48 Hz: double a0 = 1.0; double a1 = -1.999722319818149; double a2 = 0.999722358365939; double b0 = 0.999861169546022; double b1 = -1.999722339092044; double b2 = 0.999861169546022; that is used in the following direct form IIR filter implementation: double Yn, Yn1, Yn2, ...

## noise..how to regulate it?

inDear chaps, I have a problem. I have a signal recorded from a ultrasonic transducer of a chemical reaction. It is rich of noise, expecially...

Dear chaps, I have a problem. I have a signal recorded from a ultrasonic transducer of a chemical reaction. It is rich of noise, expecially the white one. I tried to filter with normal filter (butterworth band pass), but I did not obtained a lot of success. So, I thought was better delete the White gaussian noise with an adaptive filter. I used the demo of Simuling of LMS but I have probl...

## Obtaining 1/3 octave levels from a PSD

inhello i am looking for the easiest way to calculate 1/3 octave levels from an acquired signal sampled at a high rate (usually 350kHz). as i...

hello i am looking for the easiest way to calculate 1/3 octave levels from an acquired signal sampled at a high rate (usually 350kHz). as i understand it, the usual method is to create a bunch of butterworth filters and calculate the RMS level in each band, decimating occasionally to increase resolution at lower frequencies. my question is: can the 1/3 octave levels be accurately cal...

## IIR design methods

inHi all. I have come across this arcane problem where I need to filter some data, and where tests in matlab indicate that it is curcial to...

Hi all. I have come across this arcane problem where I need to filter some data, and where tests in matlab indicate that it is curcial to use a filter with no ripple in the pass band. I know of two types of digital filters that can be constructed with no ripple in the pass band, the Butterworth and Chebychev II. Now, using analog templates for designing discrete time low pass filter...

## Beginers question on nos of taps

inHi, How do the number of taps of an IIR or FIR filter corelate to the order of the filter?? Lets say I have a 2nd order Low pass Butterworth...

Hi, How do the number of taps of an IIR or FIR filter corelate to the order of the filter?? Lets say I have a 2nd order Low pass Butterworth filter, does that mean the nos of taps will be 2?? Also will the number of taps vary with the corner frequency. Thanks -Glidden This message was sent using the Comp.DSP web interface on www.DSPRelated.com

## Low Pass Reconstruction Filter

inI'm trying to build a Low Pass Reconstruction Filter for use after a DAC . The thing is it has to be a Zi = 300 Ohm input and the fc has to be...

I'm trying to build a Low Pass Reconstruction Filter for use after a DAC . The thing is it has to be a Zi = 300 Ohm input and the fc has to be 37 MHz and 50 dB attuenuation @ 118 Mhz and the passband ripple has to be < 1dB. Already tried the Butterworth but the coils were to large in fuction of the self resonant frequency of it . The Chebyshev filter has a too large ripple in th

## Cascade All Pass Filters

inHello All, Im designing and audio equalizer in Simulink. I have 15 FDATool blocks for filters with dbGain blocks after them for the gains. My...

Hello All, Im designing and audio equalizer in Simulink. I have 15 FDATool blocks for filters with dbGain blocks after them for the gains. My filters are IIR filters designed using the butterworth design method. The problem is that in the passband of my filters the phase is not perfectly linear. Could someone help instruct me on how to use matlab to design an all pass filter to linearize...

## IIR filter order

inI'm finally about ready to release an IIR filter design program called - you guessed it - ScopeIIR (TM). It currently supports the basic...

I'm finally about ready to release an IIR filter design program called - you guessed it - ScopeIIR (TM). It currently supports the basic design types of Butterworth, Chebyshev, and Elliptic. I'm trying to finalize the default and maximum IIR filter order that the program will support. To help me do that, please tell me about your experiences with IIR filter order, assuming the above t...

## Announcing ScopeIIR 5.0

inHi All, This is to announce the release of ScopeIIR 5.0, which is a comprehensive Windows tool for designing and analyzing Infinite Impulse...

Hi All, This is to announce the release of ScopeIIR 5.0, which is a comprehensive Windows tool for designing and analyzing Infinite Impulse Response (IIR) filters. The Trial Edition is free for 30 days. ScopeIIR designs high-order IIR filters based on Butterworth, Chebyshev, and Elliptic prototypes. It designs lowpass, highpass, bandpass, and bandstop filters. ScopeIIR provides a...

## Is 'Bessel' digital lowpass filter standard?

inHi, I'm trying to design a simple IIR lowpass filter with the following specs: fs = 2.4kHz fc = 150Hz order = 3 or 4 The most important...

Hi, I'm trying to design a simple IIR lowpass filter with the following specs: fs = 2.4kHz fc = 150Hz order = 3 or 4 The most important aspect is that the ringing (overshoot) shouldn't be higher than about 3%. When using a 3rd order Butterworth, I get about 9% overshoot, which is too much. Someone hinted my that a Bessel filter would be better suited. This program is a good start http:...

## butterworth filter

inHello I am an engineering student, relatively new with filters and matlab, I need to design a bandpass butterwoth filter with 2 bands in matlab...

Hello I am an engineering student, relatively new with filters and matlab, I need to design a bandpass butterwoth filter with 2 bands in matlab using the buttord function. I know how to do it for just one band and iwas trying to apply the same approach using 2 bands but i did not work. My questions are: Do i have to design 2 separated bandpass filters and combine them or is there a way do it toget...

## Adjustable Gauss Polynomial

inFor those interested in filter design, I want to introduce you to the Adjustable Gauss Polynomial. I am not selling anything here, and I...

For those interested in filter design, I want to introduce you to the Adjustable Gauss Polynomial. I am not selling anything here, and I would imagine you could implement this in MatLab if you wanted to. A couple of years ago I was experimenting with polynomial filters such as the Butterworth. My goal was to find a polynomial that was more compatible with digital filter design. One thing I t...