Quote from: aero on 07/03/2015 09:57 pmAero: do you have any gaps through which evanescent waves can escape? when you had an evanescent wave field in the past, was it achieved through intentional gaps you had placed on purpose?No, there are no gaps, as is evident in the code snippet posted above.Yes, in the past my frustum was modelled as perfect metal, hence intentional gaps were the only method to allow evanescent waves to escape. I did model the Copper Kettle with perfect metal and the gasket they had used at one point. See image attached. I don't remember anything more about that gasket, but it did make a pretty picture If there are no gaps, and (assuming that Meep is not modeling any quantum tunneling and/or that the walls are too thick for quantum tunneling to take place) then the asymmetric Poynting vector in the model must be getting dissipated into the copper (eventually resulting into heat). Currents are magnetically induced in the walls by the electromagnetic field, and these currents will meet resistance (eventually dissipating) energy into heat.Is there a way to look into the current into the walls in Meep ?
Aero: do you have any gaps through which evanescent waves can escape? when you had an evanescent wave field in the past, was it achieved through intentional gaps you had placed on purpose?No, there are no gaps, as is evident in the code snippet posted above.Yes, in the past my frustum was modelled as perfect metal, hence intentional gaps were the only method to allow evanescent waves to escape. I did model the Copper Kettle with perfect metal and the gasket they had used at one point. See image attached. I don't remember anything more about that gasket, but it did make a pretty picture
I don't know if there is the same issue here because I haven't read the forum in a while, but there seems to be a bit of a misconception on the Poynting vector and what it indicates over on the reddit forum.Alot of people seem to have confused the idea of a net, non-zero time averaged poynting vector with a net thrust. ...A net poynting vector, even averaged over all time, is NOT indicative of a net force. Force is the rate of change of the poynting vector, so a constant force would have to come from a monotonically increasing poynting vector, such that at any given time step we would need to see a poynting vector greater than the time step before.I want to stress this point because this is something I've personally stumbled over too many times.
Quote from: Rodal on 07/03/2015 11:16 pmQuote from: aero on 07/03/2015 09:57 pmAero: do you have any gaps through which evanescent waves can escape? when you had an evanescent wave field in the past, was it achieved through intentional gaps you had placed on purpose?No, there are no gaps, as is evident in the code snippet posted above.Yes, in the past my frustum was modelled as perfect metal, hence intentional gaps were the only method to allow evanescent waves to escape. I did model the Copper Kettle with perfect metal and the gasket they had used at one point. See image attached. I don't remember anything more about that gasket, but it did make a pretty picture If there are no gaps, and (assuming that Meep is not modeling any quantum tunneling and/or that the walls are too thick for quantum tunneling to take place) then the asymmetric Poynting vector in the model must be getting dissipated into the copper (eventually resulting into heat). Currents are magnetically induced in the walls by the electromagnetic field, and these currents will meet resistance (eventually dissipating) energy into heat.Is there a way to look into the current into the walls in Meep ?I'm not sure how meep can or would model Evanescent EM waves. I'm sure they use it for light but... How about a simple test to see if we can see a EM evanescent waves form with meep. A thin piece of copper ~2um thick with a 2.45GHz dipole on one side ~.12 m X and Y at a 12 to even 45 degree reflective angle and the dipole parallel 1/4 wave from the copper sheet.What do you think?
Quote from: SeeShells on 07/03/2015 11:40 pmQuote from: Rodal on 07/03/2015 11:16 pmQuote from: aero on 07/03/2015 09:57 pmAero: do you have any gaps through which evanescent waves can escape? when you had an evanescent wave field in the past, was it achieved through intentional gaps you had placed on purpose?No, there are no gaps, as is evident in the code snippet posted above.Yes, in the past my frustum was modelled as perfect metal, hence intentional gaps were the only method to allow evanescent waves to escape. I did model the Copper Kettle with perfect metal and the gasket they had used at one point. See image attached. I don't remember anything more about that gasket, but it did make a pretty picture If there are no gaps, and (assuming that Meep is not modeling any quantum tunneling and/or that the walls are too thick for quantum tunneling to take place) then the asymmetric Poynting vector in the model must be getting dissipated into the copper (eventually resulting into heat). Currents are magnetically induced in the walls by the electromagnetic field, and these currents will meet resistance (eventually dissipating) energy into heat.Is there a way to look into the current into the walls in Meep ?I'm not sure how meep can or would model Evanescent EM waves. I'm sure they use it for light but... How about a simple test to see if we can see a EM evanescent waves form with meep. A thin piece of copper ~2um thick with a 2.45GHz dipole on one side ~.12 m X and Y at a 12 to even 45 degree reflective angle and the dipole parallel 1/4 wave from the copper sheet.What do you think?Analysis of evanescent fiber optic sensors using Meep as a simulation toolhttp://www.researchgate.net/publication/262955603_Analysis_of_evanescent_fiber_optic_sensors_using_Meep_as_a_simulation_toolBloch Modes and Evanescent Modes of Photonic Crystalshttp://www.mdpi.com/2073-4352/5/1/14/pdf
.....Makes me think that "Brass" used by Juan Yang may be better than copper. It's resistivity is 5x higher, and a superconductor may not work as well. Based on this, longer and less taper is better, but I have not calculated an optimum design factor yet.Todd
Quote from: Rodal on 07/03/2015 11:57 pmQuote from: SeeShells on 07/03/2015 11:40 pmQuote from: Rodal on 07/03/2015 11:16 pmQuote from: aero on 07/03/2015 09:57 pmAero: do you have any gaps through which evanescent waves can escape? when you had an evanescent wave field in the past, was it achieved through intentional gaps you had placed on purpose?No, there are no gaps, as is evident in the code snippet posted above.Yes, in the past my frustum was modelled as perfect metal, hence intentional gaps were the only method to allow evanescent waves to escape. I did model the Copper Kettle with perfect metal and the gasket they had used at one point. See image attached. I don't remember anything more about that gasket, but it did make a pretty picture If there are no gaps, and (assuming that Meep is not modeling any quantum tunneling and/or that the walls are too thick for quantum tunneling to take place) then the asymmetric Poynting vector in the model must be getting dissipated into the copper (eventually resulting into heat). Currents are magnetically induced in the walls by the electromagnetic field, and these currents will meet resistance (eventually dissipating) energy into heat.Is there a way to look into the current into the walls in Meep ?I'm not sure how meep can or would model Evanescent EM waves. I'm sure they use it for light but... How about a simple test to see if we can see a EM evanescent waves form with meep. A thin piece of copper ~2um thick with a 2.45GHz dipole on one side ~.12 m X and Y at a 12 to even 45 degree reflective angle and the dipole parallel 1/4 wave from the copper sheet.What do you think?Analysis of evanescent fiber optic sensors using Meep as a simulation toolhttp://www.researchgate.net/publication/262955603_Analysis_of_evanescent_fiber_optic_sensors_using_Meep_as_a_simulation_toolBloch Modes and Evanescent Modes of Photonic Crystalshttp://www.mdpi.com/2073-4352/5/1/14/pdfI asked because there seems so little on Meep with Microwaves and Evanescent waves.https://en.wikipedia.org/wiki/Comparison_of_EM_simulation_softwarehttps://en.wikipedia.org/wiki/Comparison_of_EM_simulation_softwareAdding something...https://en.wikipedia.org/wiki/Comparison_of_EM_simulation_softwareEdit...EDIT 2013-01-10: I am convinced the problem is really in PML being able to amplify the evanescent waves in the near field of the oscillator. I tried to put a thin highly lossy medium into part of the PML volume. The propagating waves are attenuated enough by PML and do not reflect. The evanescent waves which freely pervade the PML are now attenuated in the lossy medium and the simulation is eventually stable.There is one caveat: when the evanescent waves get attenuated, most of the resonances in the structure become damped. With the lossy medium or without it, one has to provide enough space around the structure if the narrow resonances are to be simulated properly! Otherwise it makes no sense to run a long simulation anyway.I have also observed the case when losses and amplification nearly cancelled out and the resonances became narrow even in a small volume. However, generally it is much more practical to allocate a great simulation volume than to fine tune the losses in PML! It would be interesting if a evanescent-wave-friendly PML could be coded in MEEP in the future.
Quote from: SeeShells on 07/04/2015 12:21 amQuote from: Rodal on 07/03/2015 11:57 pmQuote from: SeeShells on 07/03/2015 11:40 pmQuote from: Rodal on 07/03/2015 11:16 pmQuote from: aero on 07/03/2015 09:57 pmAero: do you have any gaps through which evanescent waves can escape? when you had an evanescent wave field in the past, was it achieved through intentional gaps you had placed on purpose?No, there are no gaps, as is evident in the code snippet posted above.Yes, in the past my frustum was modelled as perfect metal, hence intentional gaps were the only method to allow evanescent waves to escape. I did model the Copper Kettle with perfect metal and the gasket they had used at one point. See image attached. I don't remember anything more about that gasket, but it did make a pretty picture If there are no gaps, and (assuming that Meep is not modeling any quantum tunneling and/or that the walls are too thick for quantum tunneling to take place) then the asymmetric Poynting vector in the model must be getting dissipated into the copper (eventually resulting into heat). Currents are magnetically induced in the walls by the electromagnetic field, and these currents will meet resistance (eventually dissipating) energy into heat.Is there a way to look into the current into the walls in Meep ?I'm not sure how meep can or would model Evanescent EM waves. I'm sure they use it for light but... How about a simple test to see if we can see a EM evanescent waves form with meep. A thin piece of copper ~2um thick with a 2.45GHz dipole on one side ~.12 m X and Y at a 12 to even 45 degree reflective angle and the dipole parallel 1/4 wave from the copper sheet.What do you think?Analysis of evanescent fiber optic sensors using Meep as a simulation toolhttp://www.researchgate.net/publication/262955603_Analysis_of_evanescent_fiber_optic_sensors_using_Meep_as_a_simulation_toolBloch Modes and Evanescent Modes of Photonic Crystalshttp://www.mdpi.com/2073-4352/5/1/14/pdfI asked because there seems so little on Meep with Microwaves and Evanescent waves.https://en.wikipedia.org/wiki/Comparison_of_EM_simulation_softwarehttps://en.wikipedia.org/wiki/Comparison_of_EM_simulation_softwareAdding something...Edit...EDIT 2013-01-10: I am convinced the problem is really in PML being able to amplify the evanescent waves in the near field of the oscillator. I tried to put a thin highly lossy medium into part of the PML volume. The propagating waves are attenuated enough by PML and do not reflect. The evanescent waves which freely pervade the PML are now attenuated in the lossy medium and the simulation is eventually stable.There is one caveat: when the evanescent waves get attenuated, most of the resonances in the structure become damped. With the lossy medium or without it, one has to provide enough space around the structure if the narrow resonances are to be simulated properly! Otherwise it makes no sense to run a long simulation anyway.I have also observed the case when losses and amplification nearly cancelled out and the resonances became narrow even in a small volume. However, generally it is much more practical to allocate a great simulation volume than to fine tune the losses in PML! It would be interesting if a evanescent-wave-friendly PML could be coded in MEEP in the future.
Quote from: Rodal on 07/03/2015 11:57 pmQuote from: SeeShells on 07/03/2015 11:40 pmQuote from: Rodal on 07/03/2015 11:16 pmQuote from: aero on 07/03/2015 09:57 pmAero: do you have any gaps through which evanescent waves can escape? when you had an evanescent wave field in the past, was it achieved through intentional gaps you had placed on purpose?No, there are no gaps, as is evident in the code snippet posted above.Yes, in the past my frustum was modelled as perfect metal, hence intentional gaps were the only method to allow evanescent waves to escape. I did model the Copper Kettle with perfect metal and the gasket they had used at one point. See image attached. I don't remember anything more about that gasket, but it did make a pretty picture If there are no gaps, and (assuming that Meep is not modeling any quantum tunneling and/or that the walls are too thick for quantum tunneling to take place) then the asymmetric Poynting vector in the model must be getting dissipated into the copper (eventually resulting into heat). Currents are magnetically induced in the walls by the electromagnetic field, and these currents will meet resistance (eventually dissipating) energy into heat.Is there a way to look into the current into the walls in Meep ?I'm not sure how meep can or would model Evanescent EM waves. I'm sure they use it for light but... How about a simple test to see if we can see a EM evanescent waves form with meep. A thin piece of copper ~2um thick with a 2.45GHz dipole on one side ~.12 m X and Y at a 12 to even 45 degree reflective angle and the dipole parallel 1/4 wave from the copper sheet.What do you think?Analysis of evanescent fiber optic sensors using Meep as a simulation toolhttp://www.researchgate.net/publication/262955603_Analysis_of_evanescent_fiber_optic_sensors_using_Meep_as_a_simulation_toolBloch Modes and Evanescent Modes of Photonic Crystalshttp://www.mdpi.com/2073-4352/5/1/14/pdfI asked because there seems so little on Meep with Microwaves and Evanescent waves.https://en.wikipedia.org/wiki/Comparison_of_EM_simulation_softwarehttps://en.wikipedia.org/wiki/Comparison_of_EM_simulation_softwareAdding something...Edit...EDIT 2013-01-10: I am convinced the problem is really in PML being able to amplify the evanescent waves in the near field of the oscillator. I tried to put a thin highly lossy medium into part of the PML volume. The propagating waves are attenuated enough by PML and do not reflect. The evanescent waves which freely pervade the PML are now attenuated in the lossy medium and the simulation is eventually stable.There is one caveat: when the evanescent waves get attenuated, most of the resonances in the structure become damped. With the lossy medium or without it, one has to provide enough space around the structure if the narrow resonances are to be simulated properly! Otherwise it makes no sense to run a long simulation anyway.I have also observed the case when losses and amplification nearly cancelled out and the resonances became narrow even in a small volume. However, generally it is much more practical to allocate a great simulation volume than to fine tune the losses in PML! It would be interesting if a evanescent-wave-friendly PML could be coded in MEEP in the future.
Quote from: TheTraveller on 07/04/2015 01:23 amMy Files.Here are my files, which include every attachment (image, Pdf, Doc) Paul March uploaded to NSF.There are a few SPR documents included which are not on their web site.One very important document is the Cullen 1951 paper (in the SPR and Chinese folder). Good to review section 2.1 as it contains Cullen's equation 15, which is very much the base of Shawyer's theory as to how the momentum transfer of a EM wave, bouncing off an end plate, constrained in a microwave cavity varies as the guide wavelength varies as per the waveguide diameter, excitation mode and external Rf wavelength.https://drive.google.com/folderview?id=0B7kgKijo-p0ifk9EakZfbW9aZGMwNWZMQ01xVnBON0tkM2w0Q1NLbmtjRFFwMXBuNVlVN0U&usp=sharing<< which is very much the base of Shawyer's theory as to how the momentum transfer of a EM wave, bouncing off an end plate, constrained in a microwave cavity >>That's an incorrect statement. It is clear from Dr. Cullen's paper that his Ph.D. thesis (and the paper you referenced, which contains part of his thesis) dealt with waveguides and not with closed cavities.I was astonished to find out that Shawyer refers to Cullen's paper to defend his theory for a closed cavity, as it is clear from Dr. Cullen's paper that the formula he uses is vaiid for an open waveguide.Furthermore this is in no way "Cullen's formula", this is Maxwell's formula, as Cullen himself points out. Since some people have difficulty understanding Maxwell, Cullen pointed out in his paper to an easier, more intuitive derivation (done by somebody else much prior to Cullen, as Cullen points out) than Maxwell's derivation.
My Files.Here are my files, which include every attachment (image, Pdf, Doc) Paul March uploaded to NSF.There are a few SPR documents included which are not on their web site.One very important document is the Cullen 1951 paper (in the SPR and Chinese folder). Good to review section 2.1 as it contains Cullen's equation 15, which is very much the base of Shawyer's theory as to how the momentum transfer of a EM wave, bouncing off an end plate, constrained in a microwave cavity varies as the guide wavelength varies as per the waveguide diameter, excitation mode and external Rf wavelength.https://drive.google.com/folderview?id=0B7kgKijo-p0ifk9EakZfbW9aZGMwNWZMQ01xVnBON0tkM2w0Q1NLbmtjRFFwMXBuNVlVN0U&usp=sharing
Quote from: TheTraveller on 07/04/2015 01:39 am...Boy have you got that wrong. The guide wavelength inside a waveguide doesn't change if you close the waveguide. A frustum is a variable diameter waveguide. Such diameter adapters are used in the microwave industry all the time.Boy is it evident that you have never read Cullen's paper.
...Boy have you got that wrong. The guide wavelength inside a waveguide doesn't change if you close the waveguide. A frustum is a variable diameter waveguide. Such diameter adapters are used in the microwave industry all the time.
Quote from: TheTraveller on 07/04/2015 01:50 am...Bottom line is Shawyer is right and you are wrong.Closing a waveguide will not alter the guide wavelength, so your argument is invalid but I think you do know that.Bottom line is that ALL your posts are about promoting Shawyer.
...Bottom line is Shawyer is right and you are wrong.Closing a waveguide will not alter the guide wavelength, so your argument is invalid but I think you do know that.
Rodal and Traveler - Do we have a "Don't like" button on this forum or is that the Moderator's job?
It had never dawned on me that the x on Ex was the direction of the current. I have been alligning my Ez source antenna in the y direction thinking that in the real world, it couldn't matter. But maybe in the numerical model world? I changed direction of the antenna in the NSF-1701 copper model to the z direction, still using Ez as the source current and made a resonance run in Meep.The antenna direction does not change the resonant frequency but it increased the quality factor Q, by 40 times.I have since ran and uploaded the full set of .csv files, naming them zCopper .csv to differentiate them from the previously named Copper .csv files. They appear to have much larger numbers than before. You may wish to look at them.