From: Chris Heard ([email protected])
Date: Sun Jan 16 2000 - 17:37:22 PST
Scott,
What are the harmonics of the signal spectrum that need to be in the 5-10GHz
range in order for an additional C to take effec? When that question is
answered, the fundamental frequency and associated Tr may be implied as
well.
Chris
-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Scott McMorrow
Sent: Saturday, January 15, 2000 3:34 PM
To: [email protected]
Subject: Re: [SI-LIST] : What's your favourite Screwy SI Concept?
At least not until about 5 to 10 GHz
regareds,
scott
Lee Ritchey wrote:
> True. But is the added C significant? Answer, no!!!
>
> Tom Dagostino wrote:
>
> > Bending a wire keeps a uniform cross section. Putting a corner in a
trace
> > adds extra C at the corner from a larger area.
> >
> > Tom Dagostino
> > ICX Modeling Group
> > [email protected]
> > 503-685-1613
> >
> > -----Original Message-----
> > From: [email protected]
> > [mailto:[email protected]]On Behalf Of Jian Zheng
> > Sent: Thursday, January 13, 2000 4:33 PM
> > To: [email protected]
> > Subject: RE: [SI-LIST] : What's your favourite Screwy SI Concept?
> >
> > Hi, Doug:
> >
> > Following are the comments I would like to make on right angle corners:
> >
> > Normally, one bend should not create much radiation at relative low
> > frequency. The radiated power from a corner is normally very small
compared
> > to the transmitted power when the trace to ground plane distance is much
> > smaller than one wavelength. Assuming your signal's frequency is 1 GHz
and
> > you are using silicon substrate, one wavelength in free space is about 1
> > foot at 1 GHz. One wavelength in the silicon substrate is about 4
inches.
> > You do not need to worry about the radiation from the corners if your
> > substrate thickness is smaller than 0.2 inches (200 mils). The radiation
> > from a bend normall will be smaller than 1% of the transmitting power.
> >
> > The problem is many bends. If one corner radiates 0.1% of the power,
then 10
> > corners will radiate 1% of the power. 100 corners will radiate 10% of
the
> > power. Not only that, the biggest problem is the resonances caused by
the
> > corners. When you have multiple corners, there might be some reflection
back
> > and forth to create resonances. When a resonance happens, it is possible
> > much of the power will be radiated.
> >
> > Thanks!
> >
> > Best regards,
> >
>
> --------------------------------------------------------------------------
-- > > ------------ > > Jian-X. Zheng, Ph.D > > Zeland Software, Inc., 39676 Mission Blvd., Fremont, CA 94539, U.S.A. > > Tel: 510-797-8109, Fax: 510-797-8241, Web: http://www.zeland.com > > -------------------------------------------------------------------------- -- > > ------------ > > > > > -----Original Message----- > > > From: [email protected] > > > [mailto:[email protected]]On Behalf Of Doug McKean > > > Sent: Thursday, January 13, 2000 3:34 PM > > > To: [email protected] > > > Subject: Re: [SI-LIST] : What's your favourite Screwy SI Concept? > > > > > > > > > Well, to continue, here's another one that has > > > me scratching my head frankly. > > > > > > SI Concept: Avoid Right Angle Corners in Traces > > > > > > Underlying Concept: Right Angle Corners in traces > > > decrease signal integrity/ > > > increase emi ... > > > > > > Why It's Used: There may be some truth to it. > > > > > > Now, as far as Maxwell goes, we should see an > > > increase in radiation. But as far as I've read > > > and experimented, I just did a little mockup in > > > the chamber moments ago, the effect is minor. > > > It may in fact signify nothing. > > > > > > For instance, I take a six inch piece of wire, > > > stick it in one end of a barrel connector and > > > stick the other end of the barrel connector > > > to a coaxial cable which is connected to the > > > tracking generator of a Spectrum Analyzer. > > > This is my output. > > > > > > >From 0 to 1.3 GHz I see a particular maximized > > > profile on the SA at 3 meters. I then force a > > > sharp right angle in the wire and maximize again. > > > The profile at 3 meters has changed but slightly. > > > but, this is far field. > > > > > > I disconnect the antenna, disable the antenna > > > factors, connect directly to the SA a near > > > field probe and measure along the wire. At the > > > bend of the wire when compared to a straight > > > geometry, there is approx (very hard to tell) > > > a +3 dB increase. And there could be a host > > > of errors here. But I would expect some sort > > > of change. > > > > > > Now this might not say anything for emissions. > > > As far as a tdr in concerned, I doubt it would > > > show a significant change in impedance to worry. > > > BUT, the change in near field amplitude makes me > > > suspect a corresponding increase in crosstalk > > > (perhaps minor) say in a bus architecture. A > > > tight high speed bus architecture. > > > > > > The above experiment strictly an observation. > > > > > > Comments? - Doug McKean > > > > > > **** To unsubscribe from si-list: send e-mail to > > > [email protected]. In the BODY of message put: > > > UNSUBSCRIBE si-list, for more help, put HELP. > > > si-list archives are accessible at http://www.qsl.net/wb6tpu > > > **** > > > > > > > > > > **** To unsubscribe from si-list: send e-mail to > > [email protected]. In the BODY of message put: UNSUBSCRIBE > > si-list, for more help, put HELP. > > si-list archives are accessible at http://www.qsl.net/wb6tpu > > **** > > > > **** To unsubscribe from si-list: send e-mail to [email protected]. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. > > si-list archives are accessible at http://www.qsl.net/wb6tpu > > **** > > **** To unsubscribe from si-list: send e-mail to [email protected]. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. > si-list archives are accessible at http://www.qsl.net/wb6tpu > ****-- Scott McMorrow Principal Engineer SiQual, Signal Quality Engineering 18735 SW Boones Ferry Road Tualatin, OR 97062-3090 (503) 885-1231 http://www.siqual.com
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