[SI-LIST] Re: S-parameter passivity... Interpreting the results.
- From: "Xilei Liu" <xileil@xxxxxxxxxxx>
- To: John.Hill@xxxxxxxxxx, ray.anderson@xxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Sat, 22 Jul 2006 10:27:05 +0000
Dear John, Ray, Mike...
I am hesitating to respond to your emails. I blamed myself to have raised
this question that annoyed John in the end. I believe in John's claim of a
transistor that gives negative resistance and hence increases Q. I do thank
John to give me the two threads about enhancing Q. However, for Thread 1, it
requires a bias network; for Thread 2, even each of the balanced two
Colpitts oscillators sees half of the ESR, the ESR still absorbs power. For
our application, we don't really need very high Q if we have to pay for it.
In fact, I could not download the fulltext of John's patent. After reading
the abstract and John's emails, I have given up thinking about Q. Since John
has pointed out that he "would like to get back to the signal integrity
issues", shall we all get back to the SI issues? Sorry, John, I hope this is
the end.
Best regards,
Celine
>From: "Hill, John" <John.Hill@xxxxxxxxxx>
>Reply-To: John.Hill@xxxxxxxxxx
>To: <ray.anderson@xxxxxxxxxx>,<si-list@xxxxxxxxxxxxx>
>Subject: [SI-LIST] Re: S-parameter passivity... Interpreting the results.
>Date: Fri, 21 Jul 2006 11:28:30 -0400
>
>Ray,
>
>We are mixing the context of some of the e-mails. There are two threads
>that are being mixed together here. I am to blame for this, but there is
>a reason behind the madness. First was the idea of increasing the Q of a
>crystal with negative resistance. The second is the doubling of the Q in
>a balanced configuration of two Colpitts oscillators.=20
>
>A Colpitts oscillator works with negative resistance at the base of the
>transistor. This can be measured as a S11 that is positive. This
>provides for a loop gain that is positive even with the loss incurred in
>the resonator. In an oscillator higher Q is good as long as you are not
>concerned for the ring up time. In the balanced oscillator design, the
>losses of the single resonator are shared between the two oscillators.
>Hence the Q of the resonator as seen by each of the oscillators is
>doubled. Each oscillator sees half of the ESR.=20
>
>In the e-mail from Xilei he has not indicated that he is making an
>oscillator. Hence, a high Q may or may not be what he wants or needs.
>The point was not to be a slave to Q. It can and should be controlled.
>We should not just allow it to happen.
>
>As to your point one; yes, at resonates in the Colpitts oscillator my
>expectation is that the resistance of the bias network will be in
>parallel with the much lower ESR of the resonator.=20
>
>As to your point two; yes, my claim is that the degradation of Q due to
>the bias network is not major. The circuit fulfills the requirements of
>the application very well. Fussing over the Q of the circuit is a great
>academic subject, but has little value. After all the bias network is
>required to make the circuit work.=20
>
>The point to remember is that the ring up time of the oscillator is
>important in this application. As the Q increases, the ring up time will
>increase and that is not always good. It needs to be controlled and this
>is done by the bias network. I have not calculated the reduction in Q
>because it is not important to the application. The ring up time is more
>important and it can be measured easily.
>
>As to your point three; no, the claim is that having two oscillators 180
>degrees out of phase provides for a sharing of the ESR of the resonator
>and effectively doubles the Q as seen by each oscillator. In an
>oscillator the loop gain will be placed into compression by clipping
>until it is at unity at the frequency of oscillation. But this does
>bring up the idea that negative resistance can affect the Q of a
>network. This is the madness I referred to earlier in this e-mail. To me
>this is an interesting thought that may lead Xilei to a novel solution
>to his problem.
>
>But remember the gain is changing as the oscillator is ringing up and is
>mostly compressed when it is running. This is why analyzing oscillators
>with SPICE is not as good as using a frequency domain simulator that can
>simulate the non-linear variations in gain and junction capacitance as
>the oscillator rings up. If you think about it, the Q is changing as the
>oscillator is ringing up.
>
>As to your point four; not every circuit is improved by a higher Q. The
>point is to control the Q. The Balance Oscillator has a higher effective
>Q than a single Colpitts and hence has a higher yield and the
>manufacturing guys like that. However, it will also have the tendency to
>have a longer ring up time and that can be a problem if you allow the Q
>to get too high.=20
>
>I hope this clears thing up a bit. The idea is to control the Q and not
>to be controlled by it. Don't leave it to chance and consider that the
>right Q is what our circuits need, not high Q or low Q for that matter.=20
>
>Best regards,
>
>John
>
>
>=20
>
>---------------------------------------
>The information in this email and attachments hereto may contain legally =
>privileged, proprietary or confidential information that is intended for =
>a particular recipient. If you are not the intended recipient(s), or the =
>employee or agent responsible for delivery of this message to the =
>intended recipient(s), you are hereby notified that any disclosure, =
>copying, distribution, retention or use of the contents of this e-mail =
>information is prohibited and may be unlawful. When addressed to Takata =
>customers or vendors, any information contained in this e-mail is =
>subject to the terms and conditions in the governing contract, if =
>applicable. If you have received this communication in error, please =
>immediately notify us by return e-mail, permanently delete any =
>electronic copies of this communication and destroy any paper copies.
>---------------------------------------
>-----Original Message-----
>
>From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
>On Behalf Of Ray Anderson
>Sent: Thursday, July 20, 2006 7:01 PM
>To: si-list@xxxxxxxxxxxxx
>Cc: Ray Anderson
>Subject: [SI-LIST] Re: S-parameter passivity... Interpreting the
>results.
>
>This has been an interesting thread to follow.
>
>John, let me know if I have these items correct:
>
>1) Bias resistors (R6+R7) and (R5+R8) are in parallel and =3D3D ~ 20k =
>ohms
>
>2) You maintain that the 20K is in parallel with several ohms of ESR
>in=3D20
> the SAW resonator and will only degrade the resonator Q by a =
>very=3D20
> small amount.
>
>3) You claim that a negative resistance reflected from each transistors
>base
> effectively increases the Q of the resonator. So you have some
>increase
> in Q by means of your 'negative resistance' argument which is only
> diminished slightly by the parallel bias resistor issue.
>
>4) You mention in one of your e-mails that "the higher the Q, the harder
>it=3D20
> will be to control the circuit in production.", but in another
>message
> you say: "The manufacturing guys liked the circuit because it had
>=3D20
> a higher yield" (referring to increased resonator Q). Can you
>comment?
>
>I read through your patent and didn't notice the Q enhancement as one of
>your claims. Did I miss it or was it not claimed due to prior art or
>other considerations?
>
>
>Regards,
>
>-Ray Anderson
>
>
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
>On Behalf Of Mike Monett
>Sent: Thursday, July 20, 2006 3:24 PM
>To: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: S-parameter passivity... Interpreting the
>results.
>
>
> >Mike,
>
> > Keyless Entry systems are very popular today and most of them have
> > a Colpitts Oscillator in them. You probably have a Colpitts
> > Oscillator with the bias network you have issues with in your
> > pocket right now.
>
> > These Colpitts Oscillators work from -40 degrees C to +85. The
> > automotive industry makes a few million of these transmitters a
> > year and the warranty return rates are very low.
>
> > At RF frequencies the bias resistors you are identifying are in
> > parallel with the resonator not series and yes they do limit the
> > Q. To be specific R6 in series with R7 along with R5 in series
> > with R8 are in parallel with the resonator. They are there to bias
> > the transistor into the active region. The circuit ends up with
> > 20,000 ohms or more in parallel with the ohms of resistance of the
> > resonator at resonance. It is not a big deal.
>
> > If you would like to address your issues with Colpitts Oscillators
> > with the current designers, I can forward an e-mail to them out
> > side of this list. However, please be specific. Your statements
> > will not hold much weight with people that have spent years
> > working full time with the Colpitts oscillator unless you are
> > specific.
>
> > I am currently doing a vision system and am back to being a
> > Digital Designer except for the EMC and SI work. So if you don't
> > mind, I would like to get back to Signal Integrity issues.
>
> >Best regards,
>
> >John
>
> John,
>
> Earlier, you claimed your patent 5,486,793 doubles the Q of the
> crystal. I asked for clarification, but your answer failed to
> support your claim.
>
> As I stated before, the Thevenin equivalent of both bias networks
> are in series with the crystal. This will significantly reduce the
> Q. You acknowledge this, but you now claim it is not a big deal.
>
> Thanks for your new information.
>
> Regards,
>
> Mike Monett
>
> Antiviral, Antibacterial Silver Solution:
> http://silversol.freewebpage.org/index.htm
> SPICE Analysis of Crystal Oscillators:
> http://silversol.freewebpage.org/spice/xtal/clapp.htm
> Noise-Rejecting Wideband Sampler:
> http://www3.sympatico.ca/add.automation/sampler/intro.htm
>------------------------------------------------------------------
>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 FAQ wiki page is located at:
> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>
>List technical documents are available at:
> http://www.si-list.org
>
>List archives are viewable at: =3D20
> //www.freelists.org/archives/si-list
>or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
>Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
> =3D20
>
>
>
>------------------------------------------------------------------
>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 FAQ wiki page is located at:
> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>
>List technical documents are available at:
> http://www.si-list.org
>
>List archives are viewable at: =20
> //www.freelists.org/archives/si-list
>or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
>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 FAQ wiki page is located at:
> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>
>List technical documents are available at:
> http://www.si-list.org
>
>List archives are viewable at:
> //www.freelists.org/archives/si-list
>or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
>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 FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
