## Forums Search for: Butterworth

## help needed for Butterworth crossover response

inHi all, I implemented a butterworth crossover with the matlab (code given below). The code is working perfectly for a 4th order butterworth...

Hi all, I implemented a butterworth crossover with the matlab (code given below). The code is working perfectly for a 4th order butterworth crossover(i.e. 24 dB/Octave). Th added response for the lowpass and high pass filters of the butterworth crossover gives 3 dB increase at the corner frequency which is expected. But the same is not obtained when i use 2nd and 3rd order butterworth fi...

## Re: Filter design with 'freqsamp' method?

in> > > Pete Fraser wrote: > > > "Vladimir Vassilevsky" wrote in message > > news:0Jidnc3knONVbbbRnZ2dnUVZ_oSdnZ2d@giganews.com... >...

> > > Pete Fraser wrote: > > > "Vladimir Vassilevsky" wrote in message > > news:0Jidnc3knONVbbbRnZ2dnUVZ_oSdnZ2d@giganews.com... > > > > > > > But why would anyone want to emulate Butterworth magnitude response in a > > > linear phase FIR filter whereas it is very straightforward to do the > > > (**exact) Butterworth as IIR filter? > > > > > > Butterworth will be one of sev

## General implementation of Butterworth filter questions

inHaving used up 5 days already, cutting and pasting the internet source code for Butterworth filters, only to have the audio spectrum analyzer show...

Having used up 5 days already, cutting and pasting the internet source code for Butterworth filters, only to have the audio spectrum analyzer show a terrible mess, I have to drop back to first principles in order to get something to work correctly. 1. I have the general Butterworth normalized polynomials for order-n (or can generate them) See http://en.wikipedia.org/wiki/Butterworth_filter ...

## Sigma-Delta Modulation into Butterworth Filter versus Ideal Lowpass Filter

inI have been experimenting with a Butterworth filter. I must be making a mistake. Here is my problem. The impulse response of the first order...

I have been experimenting with a Butterworth filter. I must be making a mistake. Here is my problem. The impulse response of the first order Butterworth filter is a decaying one-sided exponential. Suppose that the filter is 1/(1 + j f/fc ). Then, the impulse response is 2 pi fc exp(-(2 pi fc) t) u(t). Here pi = 3.14159... u(t) is the unit step. fc is the cutoff frequency. The inpu...

## Butterworth

inButterworth-like 3rd order LPF. Super slim. // (c) VLV //Fc ~ Fs/1400 //Dynamic range ~ 140 dB s32 LPF(s32 *z, s32 x) { x = z[0] +=...

Butterworth-like 3rd order LPF. Super slim. // (c) VLV //Fc ~ Fs/1400 //Dynamic range ~ 140 dB s32 LPF(s32 *z, s32 x) { x = z[0] += (x - z[0]) > > 8; x -= z[2] < < 1; z[1] += (x - z[1]) > > 8; return z[2] += (z[1] - z[2]) > > 8; } Vladimir Vassilevsky DSP and Mixed Signal Designs www.abvolt.com

## damping in biquads for butterworth filter?

inHi, I've been working on trying to implement a 4rth order butterworth from 2 biquads. I know the coefficients for these two filters will not...

Hi, I've been working on trying to implement a 4rth order butterworth from 2 biquads. I know the coefficients for these two filters will not be the same because then I get Linkwitz-Riley which I do not want. I looked through some old threads and someone pointed out that the Fc of each of the two necessary biquads will be the same, however the Q factor of each will be different. Someone ...

## Symmetry of Butterworth gain

inGreetings, I am exploring Butterworth filters on Matlab. I created the filter weights using: [b,a]=butter(8,[.6438 .9328]); Now, I want...

Greetings, I am exploring Butterworth filters on Matlab. I created the filter weights using: [b,a]=butter(8,[.6438 .9328]); Now, I want to plot the gain of the filter using the following code given below. I plotted the gain using plot(abs(H)). I do not see symmetry in the plot. My co-worker created a similar Butterworth filter using a different technique, and his plot shows symmetry. ...

## variable gain in an Butterworth IIR

inHi, I'm not sure this has been hashed out before on comp.dsp, I searched the archives but no luck. so I'll ask: I'm designing a...

Hi, I'm not sure this has been hashed out before on comp.dsp, I searched the archives but no luck. so I'll ask: I'm designing a butterworth filter using the typical analog prototype, then converting it to LP/HP/BP/BS, then doing the bilinear transform then separating out the zeros/poles into biquad sections. So far so good (if I want maximum attenuation in my stop bands), but what if...

## Who are Butterworth filters named after ?

inHi, I'm trying to dig some more info about Butterworth guy, that certaing group of IIR filters are named after. There are a lot of...

Hi, I'm trying to dig some more info about Butterworth guy, that certaing group of IIR filters are named after. There are a lot of Butterworths in the history, so I'm curious which one is right... Thanks in advance, regards, Robert.

## Re: delay added by matlab butterworth filter

inDirk, I think it depends on how one construes "delay". A _real_ Butterworth filte= r (as distinguished from a digital approximation) exhibits...

Dirk, I think it depends on how one construes "delay". A _real_ Butterworth filte= r (as distinguished from a digital approximation) exhibits a response as so= on as an input is applied. It may be small enough to go unnoticed, but it's= there. Was Rune splitting hairs? Jerry

## EVRC/butterworth filter

inIs there somewhere a free code of a EVRC coodec? Or at least a sample of the first 6th order Butterworth filter? Gerard

Is there somewhere a free code of a EVRC coodec? Or at least a sample of the first 6th order Butterworth filter? Gerard

## Help with Butterworth Filter

inHi All, I've been plowing through pages of theory in dsp books trying to work out how to create a butterworth filter. They all seem to...

Hi All, I've been plowing through pages of theory in dsp books trying to work out how to create a butterworth filter. They all seem to use different symbols and many different forms of the same equation. Lots of theory but very little of practical examples. Basically I have a series of 1500 points taken at even intervals. Let's call it f(t). Eg t f(t) 1 3412 2 3432 3 ...

## design a digital butterworth filter using matlab??

inDear members: In the demo in my class, my prof uses matlab to design a digital butterworth filter. He first designs an analog filter using...

Dear members: In the demo in my class, my prof uses matlab to design a digital butterworth filter. He first designs an analog filter using funtion butter(, , 's') and then uses bilinear transformation to convert the analog filter to a digital filter. Since I know MATLAB function butter()allows us to directly design a digital butterworth filter, I am wondering what are the advantages of my...

## biquad over butter

inHi all. I am trying to understand what the benefit would be of having a biquad instead of a butterworth filter in analogue implementation. For...

Hi all. I am trying to understand what the benefit would be of having a biquad instead of a butterworth filter in analogue implementation. For example, if I assume that -more or less- i need 2 integrating capacitor per pole, then i need the same for both a 8th order butterworth or a 4th order biquad (e.g. a OZGF). Therefore, they have the same cost, right? Is there any application where a biquad ...

## butterworth filter on pcb?

inHi: I've built a simple 2-pole low-pass Butterworth filter (maximally flat magnitude filter) with a cutoff frequency of 1kHz. I built it out...

Hi: I've built a simple 2-pole low-pass Butterworth filter (maximally flat magnitude filter) with a cutoff frequency of 1kHz. I built it out of 741 op-amps and capacitors/resistors. What i want to know is this - can i buy a prefabricated filter like this that i can plug into a printed circuit board? I'd like to make several of my circuits but i'd rather not totally rebuild the filter ...

## zero lag Butterworth filter

inIm trying to implement a zero-lag butterworth Filtert as described in tha paper...

Im trying to implement a zero-lag butterworth Filtert as described in tha paper at http://www3.uta.edu/faculty/ricard/Grad%20Biomech/Pezzack/Robertson%20(2003)%20Design%20and%20re sponses%20of%20butterworth%20filters.pdf My understanding is that the output of the filter needs to be reversed and passed back through the filter a second time, but this time with the data in reverse. I think t

## Butterworth delay

inIncreases in analog filter order for a Butterworth filter increases its delay, correct? I've heard of methods for making up for the delay...

Increases in analog filter order for a Butterworth filter increases its delay, correct? I've heard of methods for making up for the delay incurred - sometimes referred to as running the filter both backwards and forwards. Can anyone with practical experience in this domain shed some light on the subject? Thanks, Chris

## Help: Phase Delay of Butterworth Filters

inHi All, Hoping someone can help me out. I'm working with Butterworth Filters and have some great equations for calculating the coefficients...

Hi All, Hoping someone can help me out. I'm working with Butterworth Filters and have some great equations for calculating the coefficients as a function of cut-off frequency: http://www.planetanalog.com/showArticle.jhtml?articleID=12802683&pgno=3 However I need a function which gives me the phase delay of the filter as a function of cut-off frequencies. For example, a second order ...

## Butterworth bandpass gain

inHi, I'm working on butterworth IIR filters, I have my s-plane analogue prototype and conversions to HP/BS/LP working fine and am able...

Hi, I'm working on butterworth IIR filters, I have my s-plane analogue prototype and conversions to HP/BS/LP working fine and am able to calculate gain and scale it correctly, do bilinear and covert to SOS, no problem. I'm having trouble finding references about how to calculate an overall gain for the bandpass case. Is there any reference or paper that could shed some light ? Apparently,...

## delay added by matlab butterworth filter

inHi everyone, I searched around and couldnt quite find a problem like this, so sorry if there is a similar post already. In matlab I generate a...

Hi everyone, I searched around and couldnt quite find a problem like this, so sorry if there is a similar post already. In matlab I generate a simple 4th order butterworth filter, code below: [B,A]=butter(4,Wn,'low'); yf=filter(B,A,y); Where 0.0 < Wn < 1.0, with 1.0 corresponding to half the sample rate. My question is ... how do I calculate the delay added by the filter? By