[SI-LIST] Re: Insertion Loss of Passive Components
- From: agathon <hreidmarkailen@xxxxxxxxx>
- To: ryan.satrom@xxxxxxxxxxx
- Date: Sat, 16 Dec 2006 14:12:14 -0800
Ryan,
I would submit that it really ought to help. And, sorry, but please don't
claim that for SI Engineers in general. :-)
All the laws of physics rule, not just some.
The net IS a filter. And, if the section (170mil) is electrically short,
then lumped "filter" modeling could be a perfectly appropriate way to
understand and accurately model its interaction with the rest of the net.
It is a well known technique in any college microwave advanced text. In
that case, the "propagation" is irrelevant and, if resonance is at work, the
variable t, for time, itself is irrelevant. So, time to understand
filters.
On the other hand, I didn't read any convincing explanation of a "resonance"
on a bare diff pair with mismatched conductor lengths. Most likely, the
higher loss of the pair was due to mode conversion due to the mismatch,
fixed mostly by the adjustment presented by the connector lead lengths,
which WOULD be simply a correction of unequal flight times -- most easily
viewed as a propagation issue; ie: time domain.
On 12/13/06, ryansatrom <ryan.satrom@xxxxxxxxxxx> wrote:
>
> John-
>
> You are correct. As an SI Engineer, it doesn't help my understanding
> to view a net as a filter. But that doesn't make it invalid.
>
> Thanks for the insight.
>
> Ryan Satrom
>
>
> --- In si-list@xxxxxxxxxxxxxxx, "Hill, John" <John.Hill@...> wrote:
> >
> > Ryan,
> >
> > I would summit to you that not all filters use lumped elements.
> Strip
> > line filters are just lengths of coupled transmission lines and they
> > make very good microware filters.=3D20
> >
> > You can also consider a length of coupled transmission lines as two
> > transmission lines with crosstalk. The vantage point depends a lot
> on if
> > you are an SI engineer or an RF engineer.=3D20
> >
> > Best regards,
> >
> > John =3D20
> >
> > John Hill
> > Design Engineer
> > TK HOLDINGS INC =3D20
> > Electronics=3D20
> > 27200 Haggerty Road Suite B-12 =3D20
> > Farmington Hills, MI 48331
> > Office Phone: 248 699 2915
> > Mobile Phone 248 765 3599
> >
> >
> >
> > =3D20
> >
> > ---------------------------------------
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> > privileged, proprietary or confidential information that is
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> > a particular recipient. If you are not the intended recipient(s),
> or the =3D
> > employee or agent responsible for delivery of this message to the =3D
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> mail =3D
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> Takata =3D
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> > immediately notify us by return e-mail, permanently delete any =3D
> > electronic copies of this communication and destroy any paper
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> > ---------------------------------------
> > -----Original Message-----
> >
> > From: si-list-bounce@... [mailto:si-list-bounce@...]
> > On Behalf Of ryansatrom
> > Sent: Wednesday, December 13, 2006 10:50 AM
> > To: si-list@...
> > Subject: [SI-LIST] Re: Insertion Loss of Passive Components
> >
> > All-
> >
> > Thanks for your insight. I resolved the issue. To those who are=3D20
> > interested, the differential trace model included one trace that
> was=3D20
> > approximately 170mils longer than the other trace. The connector=3D20
> > launch, due to its geometry, had that same trace 170mils shorter
> than=3D20
> > the other trace. So when I measured differential insertion loss,=3D20
> > there was a resonance due to the length mismatch on both of the=3D20
> > subcircuits. However, they pieced together and the resonance was=3D20
> > removed, causing improved insertion loss.
> >
> > John - I like your filter analogy, but I believe that the analogy=3D20
> > breaks down when we become concerned about transmission lines (and
> EM=3D20
> > waves) and not lumped elements. It does little to feed our
> intuition=3D20
> > as to how an electromagnetic wave travels down a trace. It is an=3D20
> > analog world, but it's also an electromagnetic world:)
> >
> > --- In si-list@xxxxxxxxxxxxxxx, "Hill, John" <John.Hill@> wrote:
> > >
> > > Ryan,
> > >=3D20
> > > Consider a filter, in the pass band the filter can have a lot of
> > > inductors and capacitors between the source and the load, but the
> > > insertion loss is low. This is because all of the inductances and
> > > capacitances resonate together without changing the real value
> of=3D20
> > the
> > > impedance.
> > >=3D20
> > > Now consider the same filter in the stop band. The inductors and
> > > capacitances do not resonate together and either changes the
> real=3D20
> > value
> > > of the filter or makes it very non-real.=3D3D3D20
> > >=3D20
> > > The point is that in the pass band the filter correctly matches
> the
> > > source impedance to the load impedance and in the stop band the=3D20
> > filter
> > > deliberately miss-matches the impedances.=3D3D3D20
> > >=3D20
> > > Look at your circuit as a filter. Is it matching or miss-
> matching=3D20
> > the
> > > source to the load? Remember digital signal are wide band
> signals.=3D20
> > We
> > > typically need to design our signal paths as low pass filters
> with=3D20
> > high
> > > cutoff frequencies.
> > >=3D20
> > > As we all know, it is an analog world.
> > >=3D20
> > > Best regards,
> > >=3D20
> > > John
> > >=3D20
> > > John Hill
> > > Design Engineer
> > > TK HOLDINGS INC =3D3D3D20
> > > Electronics=3D3D3D20
> > > 27200 Haggerty Road Suite B-12 =3D3D3D20
> > > Farmington Hills, MI 48331
> > > Office Phone: 248 699 2915
> > > Mobile Phone 248 765 3599
> > >=3D20
> > >=3D20
> > > =3D3D3D20
> > >=3D20
> > > ---------------------------------------
> > > The information in this email and attachments hereto may
> contain=3D20
> > legally =3D3D3D
> > > privileged, proprietary or confidential information that is=3D20
> > intended for =3D3D3D
> > > a particular recipient. If you are not the intended recipient
> (s),=3D20
> > or the =3D3D3D
> > > employee or agent responsible for delivery of this message to the
> =3D
> > =3D3D3D
> > > intended recipient(s), you are hereby notified that any
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> > =3D3D3D
> > > copying, distribution, retention or use of the contents of this e-
> > mail =3D3D3D
> > > information is prohibited and may be unlawful. When addressed
> to=3D20
> > Takata =3D3D3D
> > > customers or vendors, any information contained in this e-mail is
> =3D
> > =3D3D3D
> > > subject to the terms and conditions in the governing contract, if
> =3D
> > =3D3D3D
> > > applicable. If you have received this communication in error,=3D20
> > please =3D3D3D
> > > immediately notify us by return e-mail, permanently delete any
> =3D3D3D
> > > electronic copies of this communication and destroy any paper=3D20
> > copies.
> > > ---------------------------------------
> > > -----Original Message-----
> > >=3D20
> > > From: si-list-bounce@ [mailto:si-list-bounce@]
> > > On Behalf Of ryansatrom
> > > Sent: Tuesday, December 12, 2006 3:49 PM
> > > To: si-list@
> > > Subject: [SI-LIST] Insertion Loss of Passive Components
> > >=3D20
> > > SI-Listers:
> > >=3D20
> > > I have set up a simulation and am very confused by the results.
> =3D20
> > I=3D3D3D20
> > > have a differential trace in series with a connector launch.
> > >=3D20
> > > I am getting very strange insertion loss results so I'm
> hoping=3D3D3D20
> > > somebody could help advise me as to whether my model is wrong,
> or=3D20
> > I=3D3D3D20
> > > am wrong.
> > >=3D20
> > > When I view the differential insertion loss of the system
> (both=3D3D3D20
> > > subcircuits in series), the loss is better (there is less loss)=3D20
> > than=3D3D3D20
> > > the differential insertion of the trace only. Is this possible?
> =3D20
> > I=3D3D3D20
> > > always thought that it was impossible to improve the insertion=3D20
> > loss=3D3D3D20
> > > by adding a passive component. And I think I still believe
> that,=3D20
> > but=3D3D3D20
> > > now I'm getting a little confused.
> > >=3D20
> > > It's also important to note that the single-ended insertion =3D
> > loss=3D3D3D20
> > > results seem to be as expected. That is, the insertion loss of=3D20
> > the=3D3D3D20
> > > system is worse than the insertion loss of either
> individual=3D3D3D20
> > > component.
> > >=3D20
> > > Is something occurring with the differential signal to allow it=3D20
> > to=3D3D3D20
> > > perform better?
> > >=3D20
> > > Please advise. Thanks in advance for your response.
> > >=3D20
> > > Ryan Satrom
> > > Everett Charles Technologies
> > > ryan.satrom@
> > >=3D20
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