# impulse response of filter

Started by April 28, 2013
```Sirs,

In many of the textbooks, the impulse response of a filter is given as a
SINC function. If we ignore the non-causal nature of the impulse response,
still the impulse response extends, in theory at least, for infinite
duration.

My question is, since the impulse response is infinite in duration, does
that mean that this represents IIR type of structure?

Thanks, manish
```
```On 4/28/2013 4:31 AM, manishp wrote:
> Sirs,
>
> In many of the textbooks, the impulse response of a filter is given as a
> SINC function. If we ignore the non-causal nature of the impulse response,
> still the impulse response extends, in theory at least, for infinite
> duration.
>
> My question is, since the impulse response is infinite in duration, does
> that mean that this represents IIR type of structure?
>
> Thanks, manish
>

http://ic.pics.livejournal.com/designfail/16613885/17655/17655_original.jpg
```
```On Sun, 28 Apr 2013 09:01:02 -0500, Vladimir Vassilevsky wrote:

> On 4/28/2013 4:31 AM, manishp wrote:
>> Sirs,
>>
>> In many of the textbooks, the impulse response of a filter is given as
>> a SINC function. If we ignore the non-causal nature of the impulse
>> response,
>> still the impulse response extends, in theory at least, for infinite
>> duration.
>>
>> My question is, since the impulse response is infinite in duration,
>> does that mean that this represents IIR type of structure?
>>
>> Thanks, manish
>>
>>
> http://ic.pics.livejournal.com/
designfail/16613885/17655/17655_original.jpg

Vladimir, you remind me of the people who would move into the rural
community where I grew up.  Developers would take a perfectly good,
productive strawberry farm and pave it over to put in a housing
development, then a bunch of new people would move into those houses and
admire the rural views out their back windows.  Then, when the next
developer came in, the people who would shout the loudest in complaint
about the loss of the "rural character" of the place would be the people

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
```
```On Sun, 28 Apr 2013 04:31:22 -0500, manishp wrote:

> Sirs,
>
> In many of the textbooks, the impulse response of a filter is given as a
> SINC function. If we ignore the non-causal nature of the impulse
> response,
> still the impulse response extends, in theory at least, for infinite
> duration.
>
> My question is, since the impulse response is infinite in duration, does
> that mean that this represents IIR type of structure?

Technically I suppose that you could say a sinc (not SINC -- "sinc" isn't
an acronym) filter is IIR.

But generally an IIR filter refers to a filter with feedback among the
states, with the consequent exponentially-dying characteristic.  Sinc
filters are handy in textbooks when you want to get a point across, but
in real use they're always approximated, and an approximate sinc is often
not the best filter to use.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com
```
```Tim Wescott wrote:
> On Sun, 28 Apr 2013 09:01:02 -0500, Vladimir Vassilevsky wrote:
>
>> On 4/28/2013 4:31 AM, manishp wrote:
>>> Sirs,
>>>
>>> In many of the textbooks, the impulse response of a filter is given as
>>> a SINC function. If we ignore the non-causal nature of the impulse
>>> response,
>>> still the impulse response extends, in theory at least, for infinite
>>> duration.
>>>
>>> My question is, since the impulse response is infinite in duration,
>>> does that mean that this represents IIR type of structure?
>>>
>>> Thanks, manish
>>>
>>>
>> http://ic.pics.livejournal.com/
> designfail/16613885/17655/17655_original.jpg
>
> Vladimir, you remind me of the people who would move into the rural
> community where I grew up.  Developers would take a perfectly good,
> productive strawberry farm and pave it over to put in a housing
> development, then a bunch of new people would move into those houses and
> admire the rural views out their back windows.  Then, when the next
> developer came in, the people who would shout the loudest in complaint
> about the loss of the "rural character" of the place would be the people
> in the newest housing development.
>

In America, it is not enough to climb the ladder of sucess. It is
necessary to burn that ladder once you have climbed it...

--
Les Cargill

```
```On 4/28/2013 10:01 AM, Tim Wescott wrote:
> On Sun, 28 Apr 2013 09:01:02 -0500, Vladimir Vassilevsky wrote:
>
>> On 4/28/2013 4:31 AM, manishp wrote:
>>> Sirs,
>>>
>>> In many of the textbooks, the impulse response of a filter is given as
>>> a SINC function. If we ignore the non-causal nature of the impulse
>>> response,
>>> still the impulse response extends, in theory at least, for infinite
>>> duration.
>>>
>>> My question is, since the impulse response is infinite in duration,
>>> does that mean that this represents IIR type of structure?
>>>
>>> Thanks, manish
>>>
>>>
>> http://ic.pics.livejournal.com/
> designfail/16613885/17655/17655_original.jpg
>
> Vladimir, you remind me of the people who would move into the rural
> community where I grew up.  Developers would take a perfectly good,
> productive strawberry farm and pave it over to put in a housing
> development, then a bunch of new people would move into those houses and
> admire the rural views out their back windows.  Then, when the next
> developer came in, the people who would shout the loudest in complaint
> about the loss of the "rural character" of the place would be the people
> in the newest housing development.

http://lurkmore.so/images/6/60/Uf004759.gif

```
```On 4/28/2013 10:12 AM, Les Cargill wrote:
> Tim Wescott wrote:
>> On Sun, 28 Apr 2013 09:01:02 -0500, Vladimir Vassilevsky wrote:
>>
>>> On 4/28/2013 4:31 AM, manishp wrote:
>>>> Sirs,
>>>>
>>>> In many of the textbooks, the impulse response of a filter is given as
>>>> a SINC function. If we ignore the non-causal nature of the impulse
>>>> response,
>>>> still the impulse response extends, in theory at least, for infinite
>>>> duration.
>>>>
>>>> My question is, since the impulse response is infinite in duration,
>>>> does that mean that this represents IIR type of structure?
>>>>
>>>> Thanks, manish
>>>>
>>>>
>>> http://ic.pics.livejournal.com/
>> designfail/16613885/17655/17655_original.jpg
>>
>> Vladimir, you remind me of the people who would move into the rural
>> community where I grew up.  Developers would take a perfectly good,
>> productive strawberry farm and pave it over to put in a housing
>> development, then a bunch of new people would move into those houses and
>> admire the rural views out their back windows.  Then, when the next
>> developer came in, the people who would shout the loudest in complaint
>> about the loss of the "rural character" of the place would be the people
>> in the newest housing development.
>>
>
>
> In America, it is not enough to climb the ladder of sucess. It is
> necessary to burn that ladder once you have climbed it...
>