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From: maury on 26 Jul 2010 10:56
On Jul 26, 6:15 am, Rune Allnor <all...(a)tele.ntnu.no> wrote:
> On 26 Jul, 04:42, HardySpicer <gyansor...(a)gmail.com> wrote:
>
>
>
>
>
> > On Jul 26, 11:22 am, Tim Wescott <t...(a)seemywebsite.com> wrote:
>
> > > On 07/25/2010 01:08 PM, fisico32 wrote:
>
> > > > Hello Forum,
>
> > > > the Paley-Wiener criterion is the  frequency equivalent of the causality
> > > > condition in the time domain.
> > > > It states that the magnitude of the transfer function can be exactly zero
> > > > only a discrete frequencies but not over a finite band of frequencies...
> > > > Why not? Is there a more conceptual explanation for that beside looking at
> > > > the integral and its derivation?
>
> > > > Realizable physical system must be causal....Is that always true?
>
> > > Name a non-causal system, then.
>
> > Duhh  - The Tardis of course!
>
> Would be surprised if our friends at the wrong side of the
> pond would be familiar with The Doctor...
>
> Dr Rune- Hide quoted text -
>
> - Show quoted text -

I have a copy of everthing from Hartnell on (at least those that were
not lost). My USB expander is a miniature Tardis.

Jelly baby, anyone?

Maurice
From: Jerry Avins on 26 Jul 2010 14:14
On 7/26/2010 7:16 AM, Rune Allnor wrote:
> On 25 Jul, 22:08, "fisico32"<marcoscipioni1(a)n_o_s_p_a_m.gmail.com>
> wrote:
>> Hello Forum,
>>
>> the Paley-Wiener criterion is the frequency equivalent of the causality
>> condition in the time domain.
>> It states that the magnitude of the transfer function can be exactly zero
>> only a discrete frequencies but not over a finite band of frequencies...
>> Why not? Is there a more conceptual explanation for that beside looking at
>> the integral and its derivation?
>
> No.

I can offer a non-rigorous explanation that is at the root of the
rigorous one.

Every exact zero in the transfer function is the result of a point zero
of that function. A zero continuum requires an infinity of point zeros.
That is difficult to achieve with limited resources.

Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
From: Rune Allnor on 26 Jul 2010 15:30
On 26 Jul, 20:14, Jerry Avins <j...(a)ieee.org> wrote:
> On 7/26/2010 7:16 AM, Rune Allnor wrote:
>
> > On 25 Jul, 22:08, "fisico32"<marcoscipioni1(a)n_o_s_p_a_m.gmail.com>
> > wrote:
> >> Hello Forum,
>
> >> the Paley-Wiener criterion is the  frequency equivalent of the causality
> >> condition in the time domain.
> >> It states that the magnitude of the transfer function can be exactly zero
> >> only a discrete frequencies but not over a finite band of frequencies....
> >> Why not? Is there a more conceptual explanation for that beside looking at
> >> the integral and its derivation?
>
> > No.
>
> I can offer a non-rigorous explanation that is at the root of the
> rigorous one.

Not at the zero...?

> Every exact zero in the transfer function is the result of a point zero
> of that function. A zero continuum requires an infinity of point zeros.
> That is difficult to achieve with limited resources.

To me, this is the same as saying that the integrand
is not analytic. Which is merely a repharsing of the
starting position, where one investigates the integral.

Rune
From: Jerry Avins on 26 Jul 2010 15:37
On 7/26/2010 3:30 PM, Rune Allnor wrote:
> On 26 Jul, 20:14, Jerry Avins<j...(a)ieee.org> wrote:
>> On 7/26/2010 7:16 AM, Rune Allnor wrote:
>>
>>> On 25 Jul, 22:08, "fisico32"<marcoscipioni1(a)n_o_s_p_a_m.gmail.com>
>>> wrote:
>>>> Hello Forum,
>>
>>>> the Paley-Wiener criterion is the frequency equivalent of the causality
>>>> condition in the time domain.
>>>> It states that the magnitude of the transfer function can be exactly zero
>>>> only a discrete frequencies but not over a finite band of frequencies...
>>>> Why not? Is there a more conceptual explanation for that beside looking at
>>>> the integral and its derivation?
>>
>>> No.
>>
>> I can offer a non-rigorous explanation that is at the root of the
>> rigorous one.
>
> Not at the zero...?
>
>> Every exact zero in the transfer function is the result of a point zero
>> of that function. A zero continuum requires an infinity of point zeros.
>> That is difficult to achieve with limited resources.
>
> To me, this is the same as saying that the integrand
> is not analytic. Which is merely a repharsing of the
> starting position, where one investigates the integral.

Ii is certainly a different way to look at the same information. I had
hoped that fisico might find it more intuitive.

Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
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