RE: [SI-LIST] : Antenna Problem on the Board

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From: Ron Miller (rmiller@brocade.com)
Date: Wed May 23 2001 - 09:49:21 PDT


The frequency content depends on the rise/fall time of the
signal. An FFT can generate the amplitude of these components from the time
domain voltage waveform(measured) and the impedance of the line, getting us
to
power, the fundamental unit.

The radiation for the different frequency components depends on the
radiation
resistance of the antenna/radiating line, which is in turn dependent on the
transmission line impedance compared to free space, and the return loss of
the reflections in the transmission line and how they are space. Depending
on the spacing different frequency components will radiate less or more.

Bottom line: This is not trivial to analyze, but with simulators it can
be done.

Ron Miller

-----Original Message-----
From: Issa, Elie [mailto:Elie.Issa@compaq.com]
Sent: Wednesday, May 23, 2001 9:19 AM
To: 'Khanh Le'; Sunil Kumar; subramanya C K
Cc: Si-List
Subject: RE: [SI-LIST] : Antenna Problem on the Board

Ok, Can you share or post the materials?

-----Original Message-----
From: Khanh Le [mailto:bastilles@yahoo.com]
Sent: Wednesday, May 23, 2001 8:00 AM
To: Sunil Kumar; subramanya C K
Cc: Si-List
Subject: Re: [SI-LIST] : Antenna Problem on the Board

 Right angled traces do not have any effects at all. I have some materials
that can prove it.

Khanh

 

 

  Sunil Kumar <sunilb@cdotb.ernet.in> wrote:

Hello Subramanya

As the bandwidth of a digital signal depends on it's rise time
(roughly given by 0.35/rise_time), the radiation/transmission line effect
depend on the rise time.

Sunil

On Wed, 23 May 2001, subramanya C K wrote:

> Hello SI Gurus,
> I have a basic question here. We all know that "Right angled traces are
never used on PCBs" as the
> act as antennas (better antennas than the curved traces). In an article I
read that this radiation
> is due not to the frequency of the signal , but to it's rise time. Could
someone please explain me
> this theory ?
>
>
> Thanks and Regards,
> Subramanya C K
>
>

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