Filter construction kit

[MyCo]

Hi,

As I dug out my old z-Plane project for this:
http://www.dsprobotics.com/support/view ... 4035#p4021

I thought, why don't work a little more on this project. I've added some more modules that can be usefull for designing and analyzing filters (especially in z-Plane).

Filter Construction Kit (MyCo).fsm

(521.92 KiB) Downloaded 2117 times

The project is not finished, there are a lot of things that'll have to get done. Especially there is a lot of GUI stuff missing, and I'm not very keen on doing this. Maybe when I've nothing else to do and I'm in the mood for banging my had on the table.

And here is the still unfinished documentation for IIR filter design, that I started recently

IIR filter design for audio DSP programmers.zip

(914.54 KiB) Downloaded 1851 times

Maik

[tester]

Empty schematic loads (at high zoom) here?

[MyCo]

Uploaded it again.

[tester]

Now works, thanks.

[Tronic]

Really nice,
if you have desire and time MyCo,
a small example of how to use these tools in the design phase to obtain the filter.
help me and maybe others to make full use of this.

[trogluddite]

Thanks MyCo - I find code so much easier to understand and use than the maths websites - I think these will be a big help.

[tor]

Great work!

Thank you. I'm looking forward to study it closer

[MyCo]

This took me years to understand, and I used nearly all PDFs to this topic that I could find. I'm not good a higher math, wich is often used to describe the Filter design process. There are some very enlighting documents, that I've discovered, that are targeted to programmers. For me the most important one, is this:

http://yehar.com/blog/?p=121
Read the section "Pole-zero IIR filter design" and the following chapters.

From now on, you know what a z-Plane is, and you know what Poles and Zeros do. The next big step is understanding the transfer function wich is called H(z), and you have to be very carefull, there are many documents using H(s) or G(s) to describe the filter design process. Those are different equations (for s-Plane), you can transform this into H(z), using substitution, but this is not that easy. You need a lot of paper for writing this down. There are also different notations for H(z), one shows it in Pole+Zero representation, and the other shows it in coeffizient representation. In the Pole+Zero representation, you can read directly the coordinates for Poles and Zeros. In coeffizient representation, you can read directly the coeffizients that you can eg. put directly into a biquad filter formula.

For filter design using z-Plane, the task is to convert H(z) from Pole+Zero representation into coeffizient representation. You do this, because in Pole+Zero representation you can easily see and manipulate the filter response, in coeffizient representation it is impossible to do that. Here comes this toolkit in.

You drag Poles & Zeros around, and you can also see the response from this, using some of the modules I've added. Then you pass the Poles&Zeros in pairs into a biquad coefficient module. And this calculates all a0,a1,a2,b0,b1,b2 coefficients that are used in nearly all of the filters you've seen in S|M or FS.

If there is some interest, I can go on. It's fascinating when you finally understand something, where you ever thought "that's to high for me"

[tester]

I don't understand most of what you wrote, but if there is a practical application for using these results - I'm in. Understanding can come later. Eventually I rather like to know what I'm doing and why.

[stw]

http://yehar.com/blog/?p=121
Read the section "Pole-zero IIR filter design" and the following chapters.

I also used to read Olli's explanations in the past. Though i forgot most of it i remember that he really is one of the few who's able to explain hard to understand things in a manner that "braindeads" like me get the feeling of knowing what really goes on behind the scene
Absolutely recommendable!!