FIR Cookbook?
in [DSP]
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From: jeff227 on 13 Dec 2006 09:40 >Rune >Seems about the right size I would expect for a decent filter cookbook >-- a couple >of hundred pages. Rune, you are really messin' with me now! Two days ago I was slammed by both you and Vladamir who said that designing a filter was "trivial". What, then, do you mean by the above comment? As far as I can tell, designing a GOOD filter with all the desired characteristics is NOT trivial.
From: Al Clark on 13 Dec 2006 09:48 "jeff227" <rocksonics(a)earthlink.net> wrote in news:ltydnVWZwIdbjR3YnZ2dnUVZ_revnZ2d(a)giganews.com: >>Rune > >>Seems about the right size I would expect for a decent filter cookbook >>-- a couple >>of hundred pages. > > > Rune, you are really messin' with me now! Two days ago I was slammed by > both you and Vladamir who said that designing a filter was "trivial". > > What, then, do you mean by the above comment? > > As far as I can tell, designing a GOOD filter with all the desired > characteristics is NOT trivial. > Writing an FIR filter is very easy. It takes a few lines of code. Most FIR filters use coefficients determined by methods like the remez exchange or windowing. Almost everyone uses a computer program to generate coefficients based on some requirement. This is a bit different than rb-j's cookbook situation, where you can calculate cooeffcients manually. If you are new to DSP, I would suggest Rick Lyon's "Understanding Digital Signal Processing (2nd edition)" as a good place to start. -- Al Clark Danville Signal Processing, Inc. -------------------------------------------------------------------- Purveyors of Fine DSP Hardware and other Cool Stuff Available at http://www.danvillesignal.com
From: jeff227 on 13 Dec 2006 11:24 >Writing an FIR filter is very easy. It takes a few lines of code. Yes, looping through an array IS easy but that's not designing a FIR filter. The key (and the challenge) is coming up with the coefficients. There are numerous programs available (like Matlab) that can calculate coefficients but I was looking for a routine to generate them on the fly at run time. That's what this thread is about.
From: Jerry Avins on 13 Dec 2006 11:33 jeff227 wrote: >> Writing an FIR filter is very easy. It takes a few lines of code. > > > Yes, looping through an array IS easy but that's not designing a FIR > filter. The key (and the challenge) is coming up with the coefficients. > There are numerous programs available (like Matlab) that can calculate > coefficients but I was looking for a routine to generate them on the fly > at run time. > > That's what this thread is about.\ I forget. How many filters do you need? Storing the coefficients for a few dozen might use less memory than the program to calculate them. One filter with a complex shape might be replaced with a cascade of simpler shapes, each drawn from a library in ROM. that could reduce the needed memory even more. Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
From: Rune Allnor on 13 Dec 2006 11:46
jeff227 skrev: > >Rune > > >Seems about the right size I would expect for a decent filter cookbook > >-- a couple > >of hundred pages. > > > Rune, you are really messin' with me now! Two days ago I was slammed by > both you and Vladamir who said that designing a filter was "trivial". > > What, then, do you mean by the above comment? > > As far as I can tell, designing a GOOD filter with all the desired > characteristics is NOT trivial. There is a lot to be learned before you can design a filter, but once you know how, it is trivial. As you have discovered, there are plenty of details to keep track of. You need to know what factors to consider in order to get there. This book's format seems about right if it handles IIRs, FIRs, LP, HP, BP, BS and a couple of other filters, and also provides example code. Compare it to learning how to drive a car. There is a lot you need to know before you can drive a car safely on your own. First of all, you need to learn how to actually operate the vehicle, how (and when) to use controls like, lights, gear shift, accelerator, brakes etc. Then you need to learn the traffic rules, how different parties in the traffic interact. Next, you have to train on how to plan the journey downtown a city or on the highway, in blizzards or in rain etc. If your first encounter with driving a car yourself is a book that lists everything you need to be aware of, you obviously become a bit overwhelmed. However, once you actually have learned the basics about how to drive and get a little experience, driving the care becomes second nature. Normally, you are not very conscious about any such factors as listed above. Rune |