**From:** Chris Rokusek (*[email protected]*)

**Date:** Tue Jun 05 2001 - 10:36:09 PDT

**Next message:**Rob Hinz: "Re: [SI-LIST] : Shielding Effectivness Question"**Previous message:**Ritchey Lee: "Re: [SI-LIST] : MECL System Design Handbook"**In reply to:**S. Weir: "RE: [SI-LIST] : Antenna Problem on the Board"**Next in thread:**S. Weir: "RE: [SI-LIST] : Antenna Problem on the Board"**Reply:**S. Weir: "RE: [SI-LIST] : Antenna Problem on the Board"

Steve,

Please see within.

*> Chris,
*

*>
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*> I don't see how you can justify the surprise introduction of a 20 ohm
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*> driver resistance into the discussion. That reduces the incident
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*> amplitude
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*> seen by the load at the far end similarly. Is it appropriate to
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*> compare a
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*> circuit that provides 70% (Rdvr=20, Zl=50, Rload=50), against one that
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*> provides 100%, (Rdvr=20, Rser=30, Zl=50, Rload=open)?
*

Sorry if this is a surprise, I used a 20 Ohm driver in my first reply to

this thread to which no one posted any objections.

*> For your analogy of a tight "U" shaped trace, I think that model is
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*> great. But the radiating cross-sectional area does not increase. The
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*> whole point is that we are assuming TEM, and so the wave is
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*> polarized. The
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*> scalar formula you are using holds only for the perpendicular
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*> cross-section
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*> which is just the original Length * Height. Put another way, if we have
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*> two traces, A and B where the driver for A is on the left, and B
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*> is on the
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*> right, and they are close to each other, driving each line
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*> alternately will
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*> not increase E over what we get by driving one line alone.
*

Doesn't look like we are going to converge on this one. I can't convince

myself if I take 1/100th of the current and put it on 100 lines each firing

sequentially that they are not going to add in phase at some point in the

far field. Especially if I consider the extreme case where each of the

lines are electrically short such that there would be complete overlap

between firing times.

Also, no one yet has mentioned the added discontinuity in the case of series

termination whereby the wave must make a reversal? Although this is a

higher frequency effect probably on the order of the oh-so-fun-trace-corner

thread, it should also be noted.

Best Regards,

Chris Rokusek

Innoveda

*>
*

*> Regards,
*

*>
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*>
*

*> Steve.
*

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**Next message:**Rob Hinz: "Re: [SI-LIST] : Shielding Effectivness Question"**Previous message:**Ritchey Lee: "Re: [SI-LIST] : MECL System Design Handbook"**In reply to:**S. Weir: "RE: [SI-LIST] : Antenna Problem on the Board"**Next in thread:**S. Weir: "RE: [SI-LIST] : Antenna Problem on the Board"**Reply:**S. Weir: "RE: [SI-LIST] : Antenna Problem on the Board"

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