[SI-LIST] Re: EMI
- From: "Powell, Doug" <DOUG.POWELL@xxxxxxx>
- To: <sinnovate88@xxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Thu, 15 Jun 2006 10:38:40 -0700
Shekhar,
One of the first things you need to realize when working with EMI is
that there are no clear-cut rules. That said, there are some
generalizations you can make. In the case of parallel I/O, balanced
lines are generally quieter than unbalanced. Twisted pairs are usually
quieter and terminated lines are usually quieter. When I say quiet, I
mean that there is less RF noise being radiated. Certainly, synchronous
pulsing in an unbalanced line can be very noisy. Making the pulse edges
asynchronous or offset by some amount does help in that it spreads the
energy over some time.
All radiation that leaves a product is the result of a difference in
voltage impressed across some impedance (dVdT). The return path of the
noise or the total loop area around this impedance forms an antenna
which in turn radiates energy. This path is sometimes referred to a
loop area of the antenna.
There are a multitude of way this can happen and many factors that must
be considered in order to gain a full understanding of this problem.
I suggest you read the book "Noise Reduction Techniques in Electronic
Systems" by Henry W. Ott.
-Doug
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of shekhar sharma
Sent: Thursday, June 15, 2006 9:28 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] EMI
Hi,
I have a question about electromagnatic radiation.
In parallel interface, there are two conditions: when all IOs are
switiching in one direction simultaneously and IOs are switching in one
direction with some delay with each other (ie one after another).
In two above conditions which will have more EM radiation and why?
Also It will be great help from your side if you can tell me some
literature regarding to EM radiation calculation.
Thanks in advance,
Shekhar
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