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Electromagnetic Waves, Axial Symmetry
Posted Mar 16, 2017, 6:52 a.m. EDT Low-Frequency Electromagnetics 3 Replies
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Can one specify a linearly polarized incoming (plane) wave for a geometry based on axial symmetry?
For instance if the incoming wave enters along the z-axis through a surface in the x-y plane . The polarization needs to be orthogonal to the z-axis. The only options are radial polarization and azimuthal (phi) polarization, and linear combinations. Neither represents the right physics - a linear polarized beam. (Radial polarization implies a line charge, azimuthal polarization a changing magnetic field in the z-direction).
Put another way - the linearly polarized field would break the axial symmetry; to represent a linear polarization as a sum of azimuthal and radial polarizations, the components must depend on the azimuthal coordinate (phi).
Is the only solution then a full three-dimensional geometry? We are hoping to avoid this.
For instance if the incoming wave enters along the z-axis through a surface in the x-y plane . The polarization needs to be orthogonal to the z-axis. The only options are radial polarization and azimuthal (phi) polarization, and linear combinations. Neither represents the right physics - a linear polarized beam. (Radial polarization implies a line charge, azimuthal polarization a changing magnetic field in the z-direction).
Put another way - the linearly polarized field would break the axial symmetry; to represent a linear polarization as a sum of azimuthal and radial polarizations, the components must depend on the azimuthal coordinate (phi).
Is the only solution then a full three-dimensional geometry? We are hoping to avoid this.
3 Replies Last Post Mar 18, 2017, 7:07 p.m. EDT
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Posted:
8 years ago
Gilad,
indeed axial symmetry is only suitable for very specific cases in RF-electromagnetics, e.g. a dipole or a coaxial cable, not for a plane wave.
2D planar symmetry can be suitable for a plane wave. Of course anything in your model must respect the symmetry.
But to be honest, I have never used any 2D approximation in my work in RF. The real world is 3D and even a dipole needs a feed that doesn't respect axial 2D symmetry in practical applications.
Cheers
Edgar
--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
indeed axial symmetry is only suitable for very specific cases in RF-electromagnetics, e.g. a dipole or a coaxial cable, not for a plane wave.
2D planar symmetry can be suitable for a plane wave. Of course anything in your model must respect the symmetry.
But to be honest, I have never used any 2D approximation in my work in RF. The real world is 3D and even a dipole needs a feed that doesn't respect axial 2D symmetry in practical applications.
Cheers
Edgar
--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
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Posted:
8 years ago
COMSOL allows to specify the order in phi variation. Then in principle if the structure is cylindrically symmetric, the excitation can be expanded.
--
Pu, ZHANG
DTU Fotonik
Gilad,
indeed axial symmetry is only suitable for very specific cases in RF-electromagnetics, e.g. a dipole or a coaxial cable, not for a plane wave.
2D planar symmetry can be suitable for a plane wave. Of course anything in your model must respect the symmetry.
But to be honest, I have never used any 2D approximation in my work in RF. The real world is 3D and even a dipole needs a feed that doesn't respect axial 2D symmetry in practical applications.
Cheers
Edgar
--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
--
Pu, ZHANG
DTU Fotonik
Please login with a confirmed email address before reporting spam
Posted:
8 years ago
thanks!!!!!!
by the way,
does anybody know abou a comsol model of a photodiode?
i mean a tutorial or an example model?
by the way,
does anybody know abou a comsol model of a photodiode?
i mean a tutorial or an example model?