# design of iir bpf

Started by May 8, 2008
```Hi,
I have to design a 6th order IIR BPF  that will allow a multirate filter
structure with D==3.How do i start?Is there a matlab function that does
this,I mean also incorporates the multirate structure with design of an IIR
BPF like butter().I wil greatly appreciate any guidance on this.

```
```>Hi,
>I have to design a 6th order IIR BPF  that will allow a multirate filter
>structure with D==3.How do i start?Is there a matlab function that does
>this,I mean also incorporates the multirate structure with design of an
IIR
>BPF like butter().I wil greatly appreciate any guidance on this.

no matlab function does this. i think u will have to do it as a 2 step
process. so use butter, cheby1 or cheby2 functions and the ouptut of the
filter can be decimated by 3.

in case if u need more help contact me at bharat at arithos dot com

rgds
bharat pathak

Arithos Designs
www.Arithos.com

DSP Design Consultancy and Training Company.
```
```munib wrote:
> Hi,
> I have to design a 6th order IIR BPF  that will allow a multirate filter
> structure with D==3.How do i start?Is there a matlab function that does
> this,I mean also incorporates the multirate structure with design of an IIR
> BPF like butter().I wil greatly appreciate any guidance on this.
>
>
"I tried to use Matlab's domyworkforme function, and it isn't in my
edition -- what toolbox do I need to get?"

The best guidance that I can give you is this:

Owning a hammer and saw doesn't make you a carpenter.

Owning a lathe and mill doesn't make you a machinist.

Owning Matlab doesn't make you a DSP expert.

Design the IIR filter separately.  I strongly suggest that if you don't
know how to do it by hand, you learn, and do it you do it by hand a few
times before you start using Matlab.

Cascading an IIR filter with a decimate-by-three stage should be child's
play, and isn't something I'd expect any Matlab function to do (until
they come out with the domyworkforme function, in which case we'll all
be replaced by computers).

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html
```
```On Thu, 08 May 2008 05:09:47 -0500, "munib" <muneeb30772@hotmail.com>
wrote:

>Hi,
>I have to design a 6th order IIR BPF  that will allow a multirate filter
>structure with D==3.How do i start?Is there a matlab function that does
>this,I mean also incorporates the multirate structure with design of an IIR
>BPF like butter().I wil greatly appreciate any guidance on this.

Hi,
I wonder how anyone can ask you to design an
IIR filter using MATLAB when it appears that
you're unfamiliar with MATLAB.  In any case
start reading the "Signal Processing Toolbox"
manual, that you can find on the Internet.
(It's a 780-page PDF file.)
Concentrate on the first half of Chapter 2.

Once you've computed your IIR filter
output samples (variable "Sig"), you can
decimate sequence Sig using:

DecFactor = 3;
SigDec = Sig(1:DecFactor:length(Sig));

Good Luck,
[-Rick-]

```