I can find numerous calculators that provide impedance for the above structures, but are there any that give propagation velocity too?
On 20/05/2025 14:53, Mike Perkins wrote:
I can find numerous calculators that provide impedance for the above
structures, but are there any that give propagation velocity too?
After numerous failed searches I found:
 https://www.multekpcb.com/calculators/
On 5/20/2025 10:06 AM, Mike Perkins wrote:
On 20/05/2025 14:53, Mike Perkins wrote:
I can find numerous calculators that provide impedance for the above
structures, but are there any that give propagation velocity too?
After numerous failed searches I found:
  https://www.multekpcb.com/calculators/
I think the stripline would have to be pretty far off-center for the
phase velocity to be much different than c/sqrt(Er); in pen-and-paper analysis to derive the relatively simple equations for characteristic impedance, the dominant propagation mode is considered to be TEM.
If the geometry is so screwy that it can't be well-approximated by TEM
the characteristic impedance equation is wrong, also.
I don't know what "asymmetric microstrip" is..?
On 20/05/2025 15:56, bitrex wrote:
On 5/20/2025 10:06 AM, Mike Perkins wrote:
On 20/05/2025 14:53, Mike Perkins wrote:
I can find numerous calculators that provide impedance for the above
structures, but are there any that give propagation velocity too?
After numerous failed searches I found:
  https://www.multekpcb.com/calculators/
I think the stripline would have to be pretty far off-center for the
phase velocity to be much different than c/sqrt(Er); in pen-and-paper
analysis to derive the relatively simple equations for characteristic
impedance, the dominant propagation mode is considered to be TEM.
If the geometry is so screwy that it can't be well-approximated by TEM
the characteristic impedance equation is wrong, also.
I don't know what "asymmetric microstrip" is..?
I would hope the calculators cope with standard Stripline and Microstrip.
I just needed details for Asymmetric Stripline and standard Microstrip.
On 5/20/2025 11:00 AM, Mike Perkins wrote:
On 20/05/2025 15:56, bitrex wrote:
On 5/20/2025 10:06 AM, Mike Perkins wrote:
On 20/05/2025 14:53, Mike Perkins wrote:
I can find numerous calculators that provide impedance for the
above structures, but are there any that give propagation velocity
too?
After numerous failed searches I found:
  https://www.multekpcb.com/calculators/
I think the stripline would have to be pretty far off-center for the
phase velocity to be much different than c/sqrt(Er); in pen-and-paper
analysis to derive the relatively simple equations for characteristic
impedance, the dominant propagation mode is considered to be TEM.
If the geometry is so screwy that it can't be well-approximated by
TEM the characteristic impedance equation is wrong, also.
I don't know what "asymmetric microstrip" is..?
I would hope the calculators cope with standard Stripline and Microstrip.
I just needed details for Asymmetric Stripline and standard Microstrip.
In the asymmetric stripline calculator you posted the propagation delay
is calculated from the relative permittivity of the substrate alone,
just so you know it's not returning anything different for that than the standard one.
On 5/20/2025 11:15 AM, bitrex wrote:
On 5/20/2025 11:00 AM, Mike Perkins wrote:
On 20/05/2025 15:56, bitrex wrote:
On 5/20/2025 10:06 AM, Mike Perkins wrote:
On 20/05/2025 14:53, Mike Perkins wrote:
I can find numerous calculators that provide impedance for the
above structures, but are there any that give propagation velocity >>>>>> too?
After numerous failed searches I found:
https://www.multekpcb.com/calculators/
I think the stripline would have to be pretty far off-center for the
phase velocity to be much different than c/sqrt(Er); in pen-and-paper
analysis to derive the relatively simple equations for characteristic
impedance, the dominant propagation mode is considered to be TEM.
If the geometry is so screwy that it can't be well-approximated by
TEM the characteristic impedance equation is wrong, also.
I don't know what "asymmetric microstrip" is..?
I would hope the calculators cope with standard Stripline and Microstrip. >>>
I just needed details for Asymmetric Stripline and standard Microstrip.
In the asymmetric stripline calculator you posted the propagation delay
is calculated from the relative permittivity of the substrate alone,
just so you know it's not returning anything different for that than the
standard one.
IOW the phase velocity of the TEM mode is taken as a given to develop
the pen-and-paper equations for the capacitance, and and thereby the >characteristic impedance of both the symmetric and asymmetric stripline.
I can find numerous calculators that provide impedance for the above >structures, but are there any that give propagation velocity too?
I can find numerous calculators that provide impedance for the above structures, but are there any that give propagation velocity too?
On 20/05/2025 11:53 pm, Mike Perkins wrote:
I can find numerous calculators that provide impedance for the above
structures, but are there any that give propagation velocity too?
This is sort of nuts. Microstrip is on the surface of a printed circuit board. Half the field is located in the substrate and the other half in
the air above the board. It's consequently dispersive - different
frequency components propagate at different velocities.
Strip-line is buried inside a printed circuit board and propagates in
what can be a uniform environment. It's non-dispersive. A thicker layer
of the insulating substrate above the strip line than below it could
make it asymmetric, but I've no idea if this would mess up the
propagation velocity. A different insulating substrate above the strip-
line than below it presumably could make it dispersive.
On Tue, 20 May 2025 11:20:05 -0400, bitrex <user@example.net> wrote:
On 5/20/2025 11:15 AM, bitrex wrote:
On 5/20/2025 11:00 AM, Mike Perkins wrote:
On 20/05/2025 15:56, bitrex wrote:
On 5/20/2025 10:06 AM, Mike Perkins wrote:
On 20/05/2025 14:53, Mike Perkins wrote:
I can find numerous calculators that provide impedance for the
above structures, but are there any that give propagation velocity >>>>>>> too?
After numerous failed searches I found:
  https://www.multekpcb.com/calculators/
I think the stripline would have to be pretty far off-center for the >>>>> phase velocity to be much different than c/sqrt(Er); in pen-and-paper >>>>> analysis to derive the relatively simple equations for characteristic >>>>> impedance, the dominant propagation mode is considered to be TEM.
If the geometry is so screwy that it can't be well-approximated by
TEM the characteristic impedance equation is wrong, also.
I don't know what "asymmetric microstrip" is..?
I would hope the calculators cope with standard Stripline and Microstrip. >>>>
I just needed details for Asymmetric Stripline and standard Microstrip. >>>>
In the asymmetric stripline calculator you posted the propagation delay
is calculated from the relative permittivity of the substrate alone,
just so you know it's not returning anything different for that than the >>> standard one.
IOW the phase velocity of the TEM mode is taken as a given to develop
the pen-and-paper equations for the capacitance, and and thereby the
characteristic impedance of both the symmetric and asymmetric stripline.
It's not just the relative permittivity of the substrate, as part of
the EM field is in air. In some designs this is small enough to
ignore the air part, but this must be determined, not just assumed.
Joe
On 5/20/2025 11:38 AM, Joe Gwinn wrote:
On Tue, 20 May 2025 11:20:05 -0400, bitrex <user@example.net> wrote:
On 5/20/2025 11:15 AM, bitrex wrote:
On 5/20/2025 11:00 AM, Mike Perkins wrote:
On 20/05/2025 15:56, bitrex wrote:
On 5/20/2025 10:06 AM, Mike Perkins wrote:
On 20/05/2025 14:53, Mike Perkins wrote:
I can find numerous calculators that provide impedance for the >>>>>>>> above structures, but are there any that give propagation velocity >>>>>>>> too?
After numerous failed searches I found:
https://www.multekpcb.com/calculators/
I think the stripline would have to be pretty far off-center for the >>>>>> phase velocity to be much different than c/sqrt(Er); in pen-and-paper >>>>>> analysis to derive the relatively simple equations for characteristic >>>>>> impedance, the dominant propagation mode is considered to be TEM.
If the geometry is so screwy that it can't be well-approximated by >>>>>> TEM the characteristic impedance equation is wrong, also.
I don't know what "asymmetric microstrip" is..?
I would hope the calculators cope with standard Stripline and Microstrip. >>>>>
I just needed details for Asymmetric Stripline and standard Microstrip. >>>>>
In the asymmetric stripline calculator you posted the propagation delay >>>> is calculated from the relative permittivity of the substrate alone,
just so you know it's not returning anything different for that than the >>>> standard one.
IOW the phase velocity of the TEM mode is taken as a given to develop
the pen-and-paper equations for the capacitance, and and thereby the
characteristic impedance of both the symmetric and asymmetric stripline.
It's not just the relative permittivity of the substrate, as part of
the EM field is in air. In some designs this is small enough to
ignore the air part, but this must be determined, not just assumed.
Joe
The model of stripline amenable to pen-and-paper calculation has a
conductor floating between two ground planes on the z axis, and
dielectric to infinity in the xy plane, there's no field in the air in
that model.
The microstrip model has field in air and is only quasi-TEM but they're
not the same thing. What the hell is a "asymmetric microstrip" anyway?!
Not sure what y'all think these online calculators are doing. They're
just automating the kind of pen-and-paper derived equations you can find
in the textbooks, which make a number of assumptions to make the problem >tractable to closed-form analysis.
On 5/20/2025 1:59 PM, Bill Sloman wrote:
On 20/05/2025 11:53 pm, Mike Perkins wrote:
I can find numerous calculators that provide impedance for the above
structures, but are there any that give propagation velocity too?
This is sort of nuts. Microstrip is on the surface of a printed circuit
board. Half the field is located in the substrate and the other half in
the air above the board. It's consequently dispersive - different
frequency components propagate at different velocities.
Strip-line is buried inside a printed circuit board and propagates in
what can be a uniform environment. It's non-dispersive. A thicker layer
of the insulating substrate above the strip line than below it could
make it asymmetric, but I've no idea if this would mess up the
propagation velocity. A different insulating substrate above the strip-
line than below it presumably could make it dispersive.
Ya as I've been trying to explain, the propagation velocity has to be
taken as a given to make finding either the symmetric or asymmetric
stripline capacitance (and therefore Z_0) tractable to closed-form
analysis. The simple online calculators don't do shit but take it as a >constant for stripline, based on the relative permeability of the
substrate, in either the symmetric or asymmetric case.
I didn't think this required a PhD to explain but maybe you or Dr. Hobbs
or someone can explain it better than I can..
On Tue, 20 May 2025 14:53:37 +0100, Mike Perkins <spam@spam.invalid>
wrote:
I can find numerous calculators that provide impedance for the above
structures, but are there any that give propagation velocity too?
The Saturn PCB Toolkit does.
Great program, and free.
On Tue, 20 May 2025 14:09:46 -0400, bitrex <user@example.net> wrote:
On 5/20/2025 1:59 PM, Bill Sloman wrote:
On 20/05/2025 11:53 pm, Mike Perkins wrote:
The simple equations, like from the Motorola ECL book, get stupid (as
in claim negative impedances) for some cases.
On Tue, 20 May 2025 14:09:46 -0400, bitrex <user@example.net> wrote:
On 5/20/2025 1:59 PM, Bill Sloman wrote:
On 20/05/2025 11:53 pm, Mike Perkins wrote:
I can find numerous calculators that provide impedance for the above
structures, but are there any that give propagation velocity too?
This is sort of nuts. Microstrip is on the surface of a printed circuit
board. Half the field is located in the substrate and the other half in
the air above the board. It's consequently dispersive - different
frequency components propagate at different velocities.
I can probe a microstrip on a PCB and clearly see the propagation of a
clean fast edge as it moves down the board. Dispersion is not an issue
on a reasonable-sized PCB with, say, 250 ps logic edges.
On some extreme gadgets, like skinny traces on gen5 PCIe or something,
the signals at a receiver look like noisy hairballs, but adaptive
equalizers in the receivers clean them all up.
Strip-line is buried inside a printed circuit board and propagates in
what can be a uniform environment. It's non-dispersive. A thicker layer
of the insulating substrate above the strip line than below it could
make it asymmetric, but I've no idea if this would mess up the
propagation velocity. A different insulating substrate above the strip-
line than below it presumably could make it dispersive.
Ya as I've been trying to explain, the propagation velocity has to be
taken as a given to make finding either the symmetric or asymmetric
stripline capacitance (and therefore Z_0) tractable to closed-form
analysis. The simple online calculators don't do shit but take it as a
constant for stripline, based on the relative permeability of the
substrate, in either the symmetric or asymmetric case.
I didn't think this required a PhD to explain but maybe you or Dr. Hobbs
or someone can explain it better than I can..
Saturn has an extensive list of the sources and references that they
use. And it warns you if your geometry is outside the range that it
likes.
The simple equations, like from the Motorola ECL book, get stupid (as
in claim negative impedances) for some cases.
On 5/20/2025 5:39 PM, john larkin wrote:
On Tue, 20 May 2025 14:09:46 -0400, bitrex <user@example.net> wrote:
On 5/20/2025 1:59 PM, Bill Sloman wrote:
On 20/05/2025 11:53 pm, Mike Perkins wrote:
I can find numerous calculators that provide impedance for the above >>>>> structures, but are there any that give propagation velocity too?
This is sort of nuts. Microstrip is on the surface of a printed circuit >>>> board. Half the field is located in the substrate and the other half in >>>> the air above the board. It's consequently dispersive - different
frequency components propagate at different velocities.
I can probe a microstrip on a PCB and clearly see the propagation of a
clean fast edge as it moves down the board. Dispersion is not an issue
on a reasonable-sized PCB with, say, 250 ps logic edges.
On some extreme gadgets, like skinny traces on gen5 PCIe or something,
the signals at a receiver look like noisy hairballs, but adaptive
equalizers in the receivers clean them all up.
Strip-line is buried inside a printed circuit board and propagates in
what can be a uniform environment. It's non-dispersive. A thicker layer >>>> of the insulating substrate above the strip line than below it could
make it asymmetric, but I've no idea if this would mess up the
propagation velocity. A different insulating substrate above the strip- >>>> line than below it presumably could make it dispersive.
Ya as I've been trying to explain, the propagation velocity has to be
taken as a given to make finding either the symmetric or asymmetric
stripline capacitance (and therefore Z_0) tractable to closed-form
analysis. The simple online calculators don't do shit but take it as a
constant for stripline, based on the relative permeability of the
substrate, in either the symmetric or asymmetric case.
I didn't think this required a PhD to explain but maybe you or Dr. Hobbs >>> or someone can explain it better than I can..
Saturn has an extensive list of the sources and references that they
use. And it warns you if your geometry is outside the range that it
likes.
The simple equations, like from the Motorola ECL book, get stupid (as
in claim negative impedances) for some cases.
The main limiting factor in the accuracy of evaluating stripline
impedance in closed-form is not knowing the actual surface charge
density of the strip, but the relative permittivity is what it is as
there's no field outside the substrate. It's pretty straightforward to >develop the equations for an offset strip just by changing limits of >integration in e.g section 3.7 of Pozar.
Microstrip is less amenable to closed-form solutions since the field
extends outside the substrate so you have to come up with an approximate >effective permittivity depending on the particular geometry.
On Fri, 23 May 2025 10:31:27 -0400, bitrex <user@example.net> wrote:
On 5/20/2025 5:39 PM, john larkin wrote:
On Tue, 20 May 2025 14:09:46 -0400, bitrex <user@example.net> wrote:
On 5/20/2025 1:59 PM, Bill Sloman wrote:
On 20/05/2025 11:53 pm, Mike Perkins wrote:
I can find numerous calculators that provide impedance for the above >>>>>> structures, but are there any that give propagation velocity too?
This is sort of nuts. Microstrip is on the surface of a printed circuit >>>>> board. Half the field is located in the substrate and the other half in >>>>> the air above the board. It's consequently dispersive - different
frequency components propagate at different velocities.
I can probe a microstrip on a PCB and clearly see the propagation of a
clean fast edge as it moves down the board. Dispersion is not an issue
on a reasonable-sized PCB with, say, 250 ps logic edges.
On some extreme gadgets, like skinny traces on gen5 PCIe or something,
the signals at a receiver look like noisy hairballs, but adaptive
equalizers in the receivers clean them all up.
Strip-line is buried inside a printed circuit board and propagates in >>>>> what can be a uniform environment. It's non-dispersive. A thicker layer >>>>> of the insulating substrate above the strip line than below it could >>>>> make it asymmetric, but I've no idea if this would mess up the
propagation velocity. A different insulating substrate above the strip- >>>>> line than below it presumably could make it dispersive.
Ya as I've been trying to explain, the propagation velocity has to be
taken as a given to make finding either the symmetric or asymmetric
stripline capacitance (and therefore Z_0) tractable to closed-form
analysis. The simple online calculators don't do shit but take it as a >>>> constant for stripline, based on the relative permeability of the
substrate, in either the symmetric or asymmetric case.
I didn't think this required a PhD to explain but maybe you or Dr. Hobbs >>>> or someone can explain it better than I can..
Saturn has an extensive list of the sources and references that they
use. And it warns you if your geometry is outside the range that it
likes.
The simple equations, like from the Motorola ECL book, get stupid (as
in claim negative impedances) for some cases.
The main limiting factor in the accuracy of evaluating stripline
impedance in closed-form is not knowing the actual surface charge
density of the strip, but the relative permittivity is what it is as
there's no field outside the substrate. It's pretty straightforward to
develop the equations for an offset strip just by changing limits of
integration in e.g section 3.7 of Pozar.
Microstrip is less amenable to closed-form solutions since the field
extends outside the substrate so you have to come up with an approximate
effective permittivity depending on the particular geometry.
Pozar has equations that cover a full page, and then it turns out that
some if the terms occupy another page.
Simulation often works better than equations.
On 24/05/2025 1:22 am, john larkin wrote:
On Fri, 23 May 2025 10:31:27 -0400, bitrex <user@example.net> wrote:
On 5/20/2025 5:39 PM, john larkin wrote:
On Tue, 20 May 2025 14:09:46 -0400, bitrex <user@example.net> wrote:
On 5/20/2025 1:59 PM, Bill Sloman wrote:
On 20/05/2025 11:53 pm, Mike Perkins wrote:
This is sort of nuts. Microstrip is on the surface of a printed circuit >>>>>> board. Half the field is located in the substrate and the other half in >>>>>> the air above the board. It's consequently dispersive - different
I can find numerous calculators that provide impedance for the above >>>>>>> structures, but are there any that give propagation velocity too? >>>>>>
frequency components propagate at different velocities.
I can probe a microstrip on a PCB and clearly see the propagation of a >>>> clean fast edge as it moves down the board. Dispersion is not an issue >>>> on a reasonable-sized PCB with, say, 250 ps logic edges.
On some extreme gadgets, like skinny traces on gen5 PCIe or something, >>>> the signals at a receiver look like noisy hairballs, but adaptive
equalizers in the receivers clean them all up.
Strip-line is buried inside a printed circuit board and propagates in >>>>>> what can be a uniform environment. It's non-dispersive. A thicker layer >>>>>> of the insulating substrate above the strip line than below it could >>>>>> make it asymmetric, but I've no idea if this would mess up the
propagation velocity. A different insulating substrate above the strip- >>>>>> line than below it presumably could make it dispersive.
Ya as I've been trying to explain, the propagation velocity has to be >>>>> taken as a given to make finding either the symmetric or asymmetric
stripline capacitance (and therefore Z_0) tractable to closed-form
analysis. The simple online calculators don't do shit but take it as a >>>>> constant for stripline, based on the relative permeability of the
substrate, in either the symmetric or asymmetric case.
I didn't think this required a PhD to explain but maybe you or Dr. Hobbs >>>>> or someone can explain it better than I can..
Saturn has an extensive list of the sources and references that they
use. And it warns you if your geometry is outside the range that it
likes.
The simple equations, like from the Motorola ECL book, get stupid (as
in claim negative impedances) for some cases.
The main limiting factor in the accuracy of evaluating stripline
impedance in closed-form is not knowing the actual surface charge
density of the strip, but the relative permittivity is what it is as
there's no field outside the substrate. It's pretty straightforward to
develop the equations for an offset strip just by changing limits of
integration in e.g section 3.7 of Pozar.
Microstrip is less amenable to closed-form solutions since the field
extends outside the substrate so you have to come up with an approximate >>> effective permittivity depending on the particular geometry.
Pozar has equations that cover a full page, and then it turns out that
some if the terms occupy another page.
Simulation often works better than equations.
Simulation is just a computer evaluating equations. It's certainly a lot >easier to let the computer do it for you, but both approaches rely on >essentially the same set of equations.
On Mon, 26 May 2025 01:55:40 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 24/05/2025 1:22 am, john larkin wrote:
On Fri, 23 May 2025 10:31:27 -0400, bitrex <user@example.net> wrote:
On 5/20/2025 5:39 PM, john larkin wrote:
On Tue, 20 May 2025 14:09:46 -0400, bitrex <user@example.net> wrote: >>>>>
On 5/20/2025 1:59 PM, Bill Sloman wrote:
On 20/05/2025 11:53 pm, Mike Perkins wrote:
This is sort of nuts. Microstrip is on the surface of a printed circuit >>>>>>> board. Half the field is located in the substrate and the other half in >>>>>>> the air above the board. It's consequently dispersive - different >>>>>>> frequency components propagate at different velocities.
I can find numerous calculators that provide impedance for the above >>>>>>>> structures, but are there any that give propagation velocity too? >>>>>>>
I can probe a microstrip on a PCB and clearly see the propagation of a >>>>> clean fast edge as it moves down the board. Dispersion is not an issue >>>>> on a reasonable-sized PCB with, say, 250 ps logic edges.
On some extreme gadgets, like skinny traces on gen5 PCIe or something, >>>>> the signals at a receiver look like noisy hairballs, but adaptive
equalizers in the receivers clean them all up.
Strip-line is buried inside a printed circuit board and propagates in >>>>>>> what can be a uniform environment. It's non-dispersive. A thicker layer >>>>>>> of the insulating substrate above the strip line than below it could >>>>>>> make it asymmetric, but I've no idea if this would mess up the
propagation velocity. A different insulating substrate above the strip- >>>>>>> line than below it presumably could make it dispersive.
Ya as I've been trying to explain, the propagation velocity has to be >>>>>> taken as a given to make finding either the symmetric or asymmetric >>>>>> stripline capacitance (and therefore Z_0) tractable to closed-form >>>>>> analysis. The simple online calculators don't do shit but take it as a >>>>>> constant for stripline, based on the relative permeability of the
substrate, in either the symmetric or asymmetric case.
I didn't think this required a PhD to explain but maybe you or Dr. Hobbs >>>>>> or someone can explain it better than I can..
Saturn has an extensive list of the sources and references that they >>>>> use. And it warns you if your geometry is outside the range that it
likes.
The simple equations, like from the Motorola ECL book, get stupid (as >>>>> in claim negative impedances) for some cases.
The main limiting factor in the accuracy of evaluating stripline
impedance in closed-form is not knowing the actual surface charge
density of the strip, but the relative permittivity is what it is as
there's no field outside the substrate. It's pretty straightforward to >>>> develop the equations for an offset strip just by changing limits of
integration in e.g section 3.7 of Pozar.
Microstrip is less amenable to closed-form solutions since the field
extends outside the substrate so you have to come up with an approximate >>>> effective permittivity depending on the particular geometry.
Pozar has equations that cover a full page, and then it turns out that
some if the terms occupy another page.
Simulation often works better than equations.
Simulation is just a computer evaluating equations. It's certainly a lot
easier to let the computer do it for you, but both approaches rely on
essentially the same set of equations.
Sure, dumb programs just execute dumb equations. There's a lot of that online.
A proper em simulation doesn't do that. It does the basic physics.
we do a real e/m simulation to handle cases that have no textbook
equations, like impedance matching an edge-launch SMA on a 6-layer
board. Pozar didn't do that one.
We use ATLC. Works great.
Has anyone used Comsol Multiphysics for e/m simulation?
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