[SI-LIST] Re: Question on radiation limits
- From: John Barnes <jrbarnes@xxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx, AAnbazhagan@xxxxxxxxxxxxxx
- Date: Wed, 10 Jul 2002 10:12:49 -0400
Anbazhagan,
From the pictures they used a 3m chamber. The key point in my mind is
that identical measurements in a Fully Anechoic Chamber configuration
were up to 7.3dB lower than measurements made in the configuration
specified by the radiated-emission standards.
So if I was developing a product, and only had a 3m Fully Anechoic
Chamber for my radiated-emissions measurements, I'd go for > 19dB margin
against the test limits after correcting for distance:
* 7dB for Fully Anechoic Chamber to Semianechoic Chamber correlation.
* 9dB for Vertical Correction Factor (3m Semianechoic Chamber to
10m Semianechoic Chamber correlation).
* > 3dB for unit-to-unit variations, to meet the 80-80 Rule, CISPR 22
section 7.2.3 "80% confidence that 80% of the type is below the
limit".
John Barnes
dBi Corporation
http://www.dbicorporation.com/
AAnbazhagan@xxxxxxxxxxxxxx wrote:
>
> Dear Mr. Barnes,
>
> What was the test distance they used for the chamber measurements?
> Was it 3m or 10m? If 3m, was the limits set as 40dBµV/m and 47dBµV/m or 30
> dbµV/m...
>
> Thanks,
> Anbazhagan
>
>
> John Barnes
> <jrbarnes@xxxxxxxx To: si-list@xxxxxxxxxxxxx,
> AAnbazhagan@xxxxxxxxxxxxxx
> m> cc:
> Sent by: Subject: [SI-LIST] Re:
> Question on radiation limits
> si-list-bounce@fre
> elists.org
>
>
> 07/10/2002 06:45
> PM
> Please respond to
> jrbarnes
>
>
>
> Anbazhagan,
> Just last night I ran across an article
> Kiemel, Greg, "Comparing Fully Anechoic Chambers to Semianechoic
> Limits," Compliance Engineering, vol. 19 no. 3, pp. 60-65, 2002
> Annual Reference Guide.
>
> They measured a personal computer system and a comb generator in a
> Semianechoic Chamber (SAC) that meets the volumetric site attenuation
> (VSA) requirements of ANSI C63.4. Then they put ferrite tiles with
> matched absorbers on the floor to convert the chamber to a Fully
> Anechoic Chamber (FAC), without changing anything else in the test
> setup, and repeated the measurements. They discovered that the FAC
> measurements were up to 7.3dB lower than the corresponding SAC
> ~~~~~~~~~~~~~~~~~
> measurements...
>
> John Barnes
> dBi Corporation
>
> http://www.dbicorporation.com/
>
> AAnbazhagan@xxxxxxxxxxxxxx wrote:
> >
> > Dear All,
> >
> > Though it is not strictly related to signal integrity, I have a ques=
> > tion
> > on the radiation limits set by the CISPR (Eurpoean emission standard,
> > EN55022 for emission and EN55024 for immunity).
> >
> > We have a got a lab in which we did the radation test in a fully anecho=
> > ic
> > chamber at 3 m distance (Antenna to EUT horizontal distance) to get the=
> > CE
> > certification. The limit was set as 40.35 dB=B5V/m from 30MHz to 230MHz=
> > and
> > 47.35 dB=B5V/m from 230 to 1GHz.
> >
> > The same test was conducted in another lab located at a different count=
> > ry.
> > There they had set the limit as 30 dB=B5V/m and 37dB=B5V/m and the boar=
> > d failed
> > with that limits.
> >
> > Which one of the limit is correct? It was argued that the 40dB=B5V/m li=
> > mit
> > for 3m distance is valid only for OATS and not for anechoic chambers.
> >
> > Can someone clarify it.
> >
> > Thanks
> > Anbazhagan.
> >
> > =
> >
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