[SI-LIST] Re: S-parameter passivity... Interpreting the results.
- From: "Hill, John" <jhill@xxxxxxxxxx>
- To: "Xilei Liu" <xileil@xxxxxxxxxxx>, <dgun@xxxxxxxxxx>, <travissellis@xxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Thu, 29 Jun 2006 12:53:06 -0400
Celine,
To raise the Q of a resonator you need to decrease the resistive part of
the resonate structure. You can do that with a negative resistance. For
example a Colpitts oscillator presents a negative resistance to the
resonator. It is a reflective gain. When you send a forward wave into a
reflective gain the reverse wave has more power than what you put into
it. Keep the phase between the forward and reverse waves the same at the
resonate frequency of the resonator or you will pull the resonator off
frequency.=20
This is why you don't want input pins to float. Sometimes they can bias
at a point that provides reflective gain and start to oscillate with the
resonator formed by the inductance of the wire and the capacitive input
or output on the far side of the wire.
To see an application where the Q of a resonator was effectively
increased see my patent 5,486,793 issues on January 23, 1996 - Balanced
RF Oscillator and Transmitter.=20
John
-----Original Message-----
From: Xilei Liu [mailto:xileil@xxxxxxxxxxx]=20
Sent: Monday, June 26, 2006 7:08 PM
To: Hill, John; dgun@xxxxxxxxxx; travissellis@xxxxxxxxx;
si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] Re: S-parameter passivity... Interpreting the
results.
John, thanks for your reply. I get it. As you mentioned the measuring
of=20
things that can resonate, another question that is irrelevant to this
topic=20
comes to my mind, can I post it here: I am measuring something that=20
resonates at fres, and I want to amplify the resonance strength, raise Q
factor but keep the resonance frequency the same as fres, and avoid=20
increasing the input power as well. Is there any way by adding some=20
components or simple networks to fullfil it?
Best regards,
Celine
>From: "Hill, John" <jhill@xxxxxxxxxx>
>To:=20
><xileil@xxxxxxxxxxx>,<dgun@xxxxxxxxxx>,<travissellis@xxxxxxxxx>,<si-lis
t@xxxxxxxxxxxxx>
>Subject: RE: [SI-LIST] Re: S-parameter passivity... Interpreting the=20
>results.
>Date: Mon, 26 Jun 2006 11:35:09 -0400
>
>Celine,
>
>If you are measuring things at or near 50 ohms and the test fixture and
>the thing being measured will not resonate, think about the wavelength
>of the highest frequency you want to evaluate and keep the length of
the
>test fixture to 1/20 or less. If you want to make a better measurement,
>use 1/100. For example if you are working to 1GHz (Wavelength of 300mm)
>anything around 3 mm should be measured and removed from the
>measurement.
>
>If you are measuring things that can resonate in the frequency band of
>interest, then it gets tricky. You have to figure out what parasitic
>impedances can get in the way of the measurement. For example, if you
>are measuring the capacitance of an inter layer plane (Power plane to
>Ground plane capacitance) that is 10 nF and you have a via to that
plane
>that is 75 microns long. You need to remove the via from the
>measurement. This is assuming you want to evaluate the capacitance of
>the VDD to Ground Plane and not what a chip will see at the surface.
>
>If you are trying to measure the capacitance of the inner layer, you
>need to conceder where the test setup will resonate. The inductance of
a
>75 micron via (3 Mils) is near (0.075 mm * 600 pH per mm) 45 pH. This
>structure will resonate at 1/(2 PI Square Root (LC)). That is 1/(2 PI
>Square Root (45 pH * 10 nF) or 237 MHz.
>
>If you want to evaluate what a chip will see at the surface of the
board
>with a single via, you don't remove the via because that is what you
>want to evaluate. What you do is port extend to the surface of the
>board. Use a shorted connector of the same type as on the board to find
>the electrical length of the distance from the calibration plane to the
>surface of the board.
>
>Best regards,
>
>John
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
>On Behalf Of Xilei Liu
>Sent: Monday, June 26, 2006 6:34 AM
>To: dgun@xxxxxxxxxx; travissellis@xxxxxxxxx; si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: S-parameter passivity... Interpreting the
>results.
>
>Will it help if all the adapters lengths are considered in the
>calibration
>procedure such that the calibrtion plane is brought to the DUT, for
>instance, calibrate the cable together with an identical SMA connector
>and
>coaxial probe?
>
>Celine
>
>
> >From: dgun@xxxxxxxxxx
> >Reply-To: dgun@xxxxxxxxxx
> >To: si-list@xxxxxxxxxxxxx
> >Subject: [SI-LIST] Re: S-parameter passivity... Interpreting the
>results.
> >Date: Sat, 24 Jun 2006 17:10:51 -0800
> >
> >My understanding is that you are calibrating to the 3.5mm connector
>using
> >t=3D
> >he
> >85052D cal kit, then trying to measure something at the end of an
>adapter
> >a=3D
> >nd
> >length of cable. If this is the case, then I'm not surprised you see
>some
> >ripple (or "noise"). The ripple is likely due to the adapter and
length
>of
> >cable. You would need to deembed this using a model of the probe or
>some
> >so=3D
> >rt
> >of deembedding algorithm using reflects at the end of the probe.
> >
> >At a minimum, the electrical delay from the calibration plane to the
>end of
> >the probe should be calculated or measured and removed from the
> >measurement.
> >
> >--
> >Daniel
> >
> > > ----- Original Message -----
> > > From: "travis ellis" <travissellis@xxxxxxxxx>
> > > To: "Hill, John" <jhill@xxxxxxxxxx>, si-list@xxxxxxxxxxxxx
> > > Subject: [SI-LIST] Re: S-parameter passivity... Interpreting the
> >results.
> > > Date: Tue, 13 Jun 2006 09:19:29 -0700 (PDT)
> > >=3D20
> > >=3D20
> > > I'm using the 8052D broadband economy calibration kit. I've
>performed a
> >=3D
> >full 2port SOLT=3D20
> > > calibration calibrating out the cabling. All of which use 3.5mm
> >connecto=3D
> >rs. Then I attach port=3D20
> > > 2 to a 3.5mm - GPPO connector that attaches to a 0.085 gppo
>terminated
> >c=3D
> >able on one end. The=3D20
> > > other end of the cable (DUT) has a coaxial probe. Port 1 is
>attached to
> >=3D
> >an sma to gpo=3D20
> > > connector that is mounted in a brass block and ground smooth.
This
> >provi=3D
> >des a coaxial structure=3D20
> > > that I make contact to with the coaxial probe that is on the
other
>end
> >o=3D
> >f the dut.
> > >=3D20
> > > Travis
> > > "Hill, John" <jhill@xxxxxxxxxx> wrote: Travis,
> > >=3D20
> > > Which Calibration kit are you using and can you describe what is
>between
> > > the calibration plane and the thing you are trying to model? BTW,
>what
> > > RF connector are you using?
> > >=3D20
> > > Best regards,
> > >=3D20
> > > John
> > >=3D20
> > >=3D20
> > >=3D20
> > >=3D20
> > > ---------------------------------------
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> > > ---------------------------------------
> > > -----Original Message-----
> > >=3D20
> > > From: si-list-bounce@xxxxxxxxxxxxx
>[mailto:si-list-bounce@xxxxxxxxxxxxx]
> > > On Behalf Of travis ellis
> > > Sent: Tuesday, June 13, 2006 11:00 AM
> > > To: si-list@xxxxxxxxxxxxx
> > > Subject: [SI-LIST] S-parameter passivity... Interpreting the
>results.
> > >=3D20
> > > I've been taking measurements with a VNA then running them through
a
> > > passivity checker. The basis for the code was originally posted by
>Ray.
> > > I've modified it to meet my needs. Added plotting capabilities,
log
>mag
> > > format handling, and nudging of the non-passive values when only a
>few
> > > points are out of spec etc. I don't think I broke anything in the
> > > process but what I've noticed is that the eigen values of some of
my
> > > measurements are very noisy. The better measurements oscillate too
>but
> > > they trend upward with increasing frequency. The suspect
>measurements
> > > oscillate between near 0 and approximately 0.4 from point to point
> > > across the higher frequency bands. The magnitude of the
s-parameters
> > > seem to be noisy as well. I've gone through my setup to make sure
>that
> > > my cables don't have loose/bad connections. Replaced some
connectors
> > > that seemed inadequate and while things got marginally better the
> > > measurements still contained noise. The noise source seems to be
my
> > > fixturing. Unfortunately I don't think I can improve this given
my
>
> >time
> > > constraints.
> > >=3D20
> > > The only thing that I've noticed is that the time domain
> >simulations
> > > take longer than those created with a data set that isn't as
noisy.
> > >=3D20
> > >=3D20
> > > Is there a way to decide if these models are accurate enough
to
>be
> > > reliable?
> > >=3D20
> > > Regards,
> > >=3D20
> > > Travis
> >
> >
> >--=3D20
> >___________________________________________________
> >Play 100s of games for FREE! http://games.mail.com/
> >
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