[SI-LIST] Re: Skin effect and Inductance
- From: "Ransom Stephens" <ransom@xxxxxxxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Tue, 9 Oct 2012 13:06:21 -0700
It originates from Lenz's law, the minus sign in Faraday's law of induction.
There's a tidy little description in this note, "Crossing the Digital-Analog
Divide," I wrote for Agilent:
http://cp.literature.agilent.com/litweb/pdf/5991-0168EN.pdf
including the paragraphs:
It's nice to think of a PCB trace as simply the route that a signal takes
from transmitter to receiver and, at low data rates, it's not an
unreasonable concept. In the DC ideal, current flows in the conducting trace
with a constant magnetic field of cylindrical symmetry around the trace -
according to Ampere's Law. However, during logic transitions, the current
changes. Changing currents induce an electromotive force which creates eddy
currents within the conductor in a direction counter to the change -
according to Faraday's Law. The more abrupt the change, the faster the rise
or fall, therefore, the stronger the counter eddy current. At high data
rates, around 1 Gb/s, the signal current and the induced current begin to
cancel, and the net current is restricted to an ever thinner skin at the
conductor surface; the skin effect.
The skin effect increases the effective resistance and reduces the
inductance of the circuit. Enhanced resistance causes loss. Reduced
inductance alters circuit impedance in a way that depends on PCB layout.
Impedance variations change the phases of the harmonics and subharmonics.
Those phases are what give analog waveforms their sharp-edged digital
character. As the phases vary, the signal degrades and reveals its messy
analog nature.
That'll get your hands waving with a conceptual understanding, then Dudi's
steps and you'll be a master.
Ransom
_____________________________
Ransom W. Stephens, Ph.D.
Content and Analysis
www.ransomsnotes.com
Measure of Things - Science & Technology blog at Test & Measurement World:
science from the perspective of a technologist, technology from the
perspective of a scientist
Twitting @ransomstephens
LinkedIn, Facebook and all that stuff
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Antonis Orphanou
> Sent: Tuesday, October 09, 2012 11:17 AM
> To: dudi@xxxxxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Skin effect and Inductance
>
> I would concentrate on plane wave fundamentals:
> (1). how plane waves behave at the presence of lossy interfaces.
> (2). How the phase velocity and propagation constant change at the
> presence of lossy interfaces and material.
> (3). How does field penetration changes in the presence of loss.
> (3). How the above affect the field distribution in the conductor and
> hence R & L.
>
> Any EM text-book can provide you with such basics.
>
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Dudi Tash
> Sent: Tuesday, October 09, 2012 6:03 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Skin effect and Inductance
>
> Hi All,
> I'm looking for some elaborate material regarding the reason for the skin
> effect.
>
> I know all about the losses and the actual outcome, but I'd like to
> explore more about the physical reasons for the creation of the skin
> effect. My main interest is in skin effect in PCB traces.
>
> In one of the courses of one of the Guru's I was told that the skin effect
> appears due to the fact that the Inductance in the middle of the
> transmission lines are greater than the inductance on its periphery, and
> the AC signals look for lower loop inductances.
>
>
>
> 1. Can you approve this?
>
>
> 2. Are there any other links, material that you can send?
>
>
> 3. Explanations are most welcomed as well.
>
> Thanks
>
> Best Regards,
> Dgtronix Ltd. I Founder & CEO I Dudi Tash
> eFax: +972-3-7256490 I Mobile: +972-54-6345629 I Office: +972-9-9660967
> www.dgtronix-tech.com<http://www.dgtronix-tech.com/>
>
> [cid:image001.jpg@01CDA62F.31543B90]<http://www.dgtronix-tech.com/>
> [cid:image002.jpg@01CDA62F.31543B90]
>
> [cid:image003.jpg@01CDA62F.31543B90]
>
>
> *This email contains confidential and proprietary information of Dgtronix
> Ltd.*
>
>
>
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
> or to administer your membership from a web page, go to:
> //www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>
> List forum is accessible at:
> http://tech.groups.yahoo.com/group/si-list
>
> List archives are viewable at:
> //www.freelists.org/archives/si-list
>
> Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
>
>
>
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
> or to administer your membership from a web page, go to:
> //www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>
> List forum is accessible at:
> http://tech.groups.yahoo.com/group/si-list
>
> List archives are viewable at:
> //www.freelists.org/archives/si-list
>
> Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List forum is accessible at:
http://tech.groups.yahoo.com/group/si-list
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
