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Discussion Groups | Comp.DSP | IIR vs. FIR (complexity issues)

There are 3 messages in this thread.

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IIR vs. FIR (complexity issues) - 2007-07-18 11:09:00

Hi,

I would like to know on the implementation complexity issues beween
FIR Filter vs. IIR Filter (Chebyshev).
I know that IIR is more complex than FIR. But, in case of the FIR
filter has higher order number than IIR, FIR can be more complex.

If I have IIR Chebyshev 10th order vs. FIR with 59 Taps. Which one is
the most complex one?


Thanks,

Berry

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Re: IIR vs. FIR (complexity issues) - Vladimir Vassilevsky - 2007-07-18 11:24:00




b...@gmail.com wrote:

> Hi,
> 
> I would like to know on the implementation complexity issues beween
> FIR Filter vs. IIR Filter (Chebyshev).

A classic question that was answered by Rabiner.
If the goal is having the steepest frequency response and the maximum 
passband flatness, the IIR filters are more efficient then FIR.

Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

http://www.abvolt.com

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Re: IIR vs. FIR (complexity issues) - Tim Wescott - 2007-07-18 14:38:00

b...@gmail.com wrote:
> Hi,
> 
> I would like to know on the implementation complexity issues beween
> FIR Filter vs. IIR Filter (Chebyshev).
> I know that IIR is more complex than FIR. But, in case of the FIR
> filter has higher order number than IIR, FIR can be more complex.
> 
> If I have IIR Chebyshev 10th order vs. FIR with 59 Taps. Which one is
> the most complex one?
> 
No matter what you do, the IIR filter code is going to be more complex 
-- there's just more to do compared to a FIR.

Also, IIR filters are significantly more sensitive to coefficient values 
and quantization effects.  A 10th-order Chebychev filter is going to 
have some highly resonant poles, which will make it even more sensitive. 
  This means that your IIR solution will demand more precision than your 
FIR, which will add even more complexity to your algorithm.

If the book that Vladimir doesn't cover it, I'd recommend that you do 
some noise sensitivity analysis of your proposed IIR filter, then look 
at the complexity and execution time of the resulting code to make your 
decisions.

-- 

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
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