proving LTI System

Hi,

I would like to know how I can prove that the transfer function is an LTI
system.

with regards
sudhir
		
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"kjsudhir" <kjsudhir@hotmail.com> wrote in message 
news:1111avlth4gaf9d@news.supernews.com...
> Hi,
>
> I would like to know how I can prove that the transfer function is an LTI
> system.
>
> with regards
> sudhir
>
> This message was sent using the Comp.DSP web interface on
> www.DSPRelated.com
Hi khsudjir - if you can search through the archives of this newsgroup for 
threads started by Lucy you may be lucky enough to find the answer you are 
looking for.
Best of Luck - Mike

"kjsudhir" <kjsudhir@hotmail.com> wrote in message
news:1111avlth4gaf9d@news.supernews.com...
> Hi,
>
> I would like to know how I can prove that the transfer function is an LTI
> system.
>
> with regards
> sudhir
>
> This message was sent using the Comp.DSP web interface on
> www.DSPRelated.com

I believe that the transfer functions only exist for LTI systems.

Ken Davis wrote:
> "kjsudhir" <kjsudhir@hotmail.com> wrote in message
> news:1111avlth4gaf9d@news.supernews.com...
> 
>>Hi,
>>
>>I would like to know how I can prove that the transfer function is an LTI
>>system.
>>
>>with regards
>>sudhir
>>
>>This message was sent using the Comp.DSP web interface on
>>www.DSPRelated.com
> 
> 
> I believe that the transfer functions only exist for LTI systems.
> 
> 
But I've found that neophytes often use the term "transfer function" 
incorrectly.  In fact, I'm not sure that the term isn't perfectly valid 
in other contexts to mean entirely different things.

-- 

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

kjsudhir wrote:

> Hi,
> 
> I would like to know how I can prove that the transfer function is an LTI
> system.
> 
> with regards
> sudhir
> 		
> This message was sent using the Comp.DSP web interface on
> www.DSPRelated.com

Have you googled for "linear system"?

A linear system, h, is one that, for any two inputs x1 and x2 and any 
two constants A1 and A2 follows the relation:

if y1(t) = h(x1(t)) and y2(t) = h(x2(t)) then the system is linear if 
and only if h(A1*x1(t) + A2*x2(t)) = A1*y1(t) + A2*y2(t).

A system is time invariant if for any time shift t_s and any signal 
x(t), if y(t) = h(x(t)) then h(x(t - t_s)) = y(t - t_s).

So an LTI system is one that is both linear and time-invariant.

-- 

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