[SI-LIST] AW: Re: Difference between conducted and radiated emission ?
- From: "Pommerenke, David" <davidjp@xxxxxxx>
- To: <Ravinder.Ajmani@xxxxxxxxxxxxxx>, "jun feng" <junfeng.zhou@xxxxxxxxx>
- Date: Mon, 31 Mar 2008 19:10:49 -0500
Junfeng,
One additional comment on the reason for the 30 Mhz boundary between =
radiated and conducted emissions.=20
Both regulations try to prevent unwanted radiated emissions. But we know =
that EUTs that are much smaller than the wavelength will not radiate =
directly very well, but they will excite the cables and then the cables =
will radiate. Thus, it is sufficient to measure the currents on the =
cables. The 30 MHz has been set on a typical EUT size of maybe 1 m. For =
radiated and conducted immunity the boundary is set at 80 Mhz but maybe =
varied depending on the DUT size.
Regards,
David Pommerenke
University Missouri Rolla
-----Urspr=FCngliche Nachricht-----
Von: si-list-bounce@xxxxxxxxxxxxx im Auftrag von =
Ravinder.Ajmani@xxxxxxxxxxxxxx
Gesendet: Mo 3/31/2008 11:16
An: jun feng
Cc: si-list@xxxxxxxxxxxxx
Betreff: [SI-LIST] Re: Difference between conducted and radiated =
emission ?
=20
Hi Junfeng,
Your question is more appropriate for the EMC Discussion Group. However =
since I wear both the hats, I may be able to give you an answer.
The main difference between Conducted and Radiated emissions is in the=20
frequency range. Conducted emissions are measured off the power cord of =
your system between 150 kHz and 30 MHz. Radiated emissions are measured =
from 30 MHz to 1GHz and higher, depending on the highest frequency being =
generated in your system.
The main causes of conducted emissions are the switching power supplies, =
and low frequency digital circuits (which clock below 30 MHz). The =
modern=20
cores run at hundreds of MHz and even GHz, so emissions caused by =
digital=20
switching will not show up as conducted emissions. The core switching=20
will cause radiated emissions, which can couple to the outside world=20
through PCB traces, or common-mode coupling from Power and Ground =
planes.
Regards, Ravinder
Server PCB Development
Hitachi Global Storage Technologies
Email: Ravinder.Ajmani@xxxxxxxxxxxxxx
"jun feng" <junfeng.zhou@xxxxxxxxx>=20
Sent by: si-list-bounce@xxxxxxxxxxxxx
03/31/2008 04:17 AM
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Subject
[SI-LIST] Difference between conducted and radiated emission ?
Hi,
Can anyone tell me the difference between conducted and radiated=20
emission,
especially for digital circuits ?? For instance, inside a large size=20
digital
core what is responsible for the conducted and what is for radiated=20
emission
?
regards,
Junfeng
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