Modes in Waveguide

[Jack// ani]

Hi all,

What is physical significance of various different modes travelling
inside the waveguide? Why are they so critical, when talking about
confined medium, like waveguide and optic fibre. As it hardly have any
significance in free space!!

Thanks

 

[Bruce Scott TOK]

Hi all,

What is physical significance of various different modes travelling
inside the waveguide? Why are they so critical, when talking about
confined medium, like waveguide and optic fibre. As it hardly have any
significance in free space!!

Boundary conditions for the Maxwell equations...

 

[Tim Wescott]

Hi all,

What is physical significance of various different modes travelling
inside the waveguide? Why are they so critical, when talking about
confined medium, like waveguide and optic fibre. As it hardly have any
significance in free space!!

Thanks

Different modes in a waveguide roughly equate to the number of bounces
the energy has to make to travel a given distance (yes, my E&M theory
_is_ rusty). Different modes travel at different speeds, so if you have
multiple modes they'll disperse the signal, which slows your achievable
data rate (or bandwidth).

No bounces in free space means there's only one 'mode'.

 

[PD]

Hi all,

What is physical significance of various different modes travelling
inside the waveguide? Why are they so critical, when talking about
confined medium, like waveguide and optic fibre. As it hardly have any
significance in free space!!

Thanks

Which goes to show you that a *solution* to the equations that reflect
a physical law do not have to have common properties with each other or
even with the law itself. (A law may have a symmetry that the solution
does not.) Boundary conditions form additional constraints to the
solution.

PD

 

[Phil Hobbs]

Different modes in a waveguide roughly equate to the number of bounces
the energy has to make to travel a given distance (yes, my E&M theory
_is_ rusty). Different modes travel at different speeds, so if you have
multiple modes they'll disperse the signal, which slows your achievable
data rate (or bandwidth).

No bounces in free space means there's only one 'mode'.

Rusty is the word. There is a continuum of modes in free space, because
a mode is just a propagating solution of Maxwell's equations in the
given geometry. A metal guide has a whole number of modes (a positive
integer or zero), and dielectric guides have at least one guided mode
and a continuum of unguided modes. (There's no analogue of a
waveguide-below-cutoff filter in the dielectric guide world.)

Cheers,

Phil Hobbs

 

[Tim Wescott]

Rusty is the word. There is a continuum of modes in free space, because
a mode is just a propagating solution of Maxwell's equations in the
given geometry. A metal guide has a whole number of modes (a positive
integer or zero), and dielectric guides have at least one guided mode
and a continuum of unguided modes. (There's no analogue of a
waveguide-below-cutoff filter in the dielectric guide world.)

Cheers,

Phil Hobbs

Oh, right. Hermetians and all that. But the free-space modes all go
the same speed so it's not the Big Deal that it is with waveguides,
unless you're trying for a perfectly circular spot out of a laser.

Now I'm less rusty.

Thanks.

 

[Dastardly Fiend]

Hi all,

What is physical significance of various different modes travelling
inside the waveguide? Why are they so critical, when talking about
confined medium, like waveguide and optic fibre. As it hardly have any
significance in free space!!

Thanks

One word: Resonance.
Waveguides, optical fibres, coaxial cables, antennae, tuning forks, pipe
organs, flutes and oboes and even violins. Resonance.

http://hyperphysics.phy-astr.gsu.edu/hbase/waves/standw.html#c4
http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/waves/swf.gif
http://id.mind.net/~zona/mstm/physi...s/standingWaves1/StandingWaves1.htmlAndrocles.

 

[Dastardly Fiend]

Which goes to show you that a *solution* to the equations that reflect
a physical law do not have to have common properties with each other or
even with the law itself. (A law may have a symmetry that the solution
does not.) Boundary conditions form additional constraints to the
solution.

PD

The symmetry is there, you just have to find it.
http://id.mind.net/~zona/mstm/physics/waves/standingWaves/standingWaves


Androcles.

 

[Rich Grise]

One word: Resonance.
Waveguides, optical fibres, coaxial cables, antennae, tuning forks, pipe
organs, flutes and oboes and even violins. Resonance.

http://hyperphysics.phy-astr.gsu.edu/hbase/waves/standw.html#c4
http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/waves/swf.gif
http://id.mind.net/~zona/mstm/physi...s/standingWaves1/StandingWaves1.htmlAndrocles.

You've omitted "sinus cavities" and "exhaust headers". ;-)

Ever see that "Blue Man Group" bit where they've got a telescoping piece
of about 6" PVC pipe, and one guy beats on it with drumsticks while another
slides the telescoping part of the pipe in and out? Resonance.

Planetary orbits, electronic orbitals, NMR/MRI, etc, etc, etc...

Cheers!
Rich

 

[Dastardly Fiend]

You've omitted "sinus cavities" and "exhaust headers". ;-)

Ever see that "Blue Man Group" bit where they've got a telescoping piece
of about 6" PVC pipe, and one guy beats on it with drumsticks while
another
slides the telescoping part of the pipe in and out?

No.
I do know what a trombone is.
Androcles.


Resonance.

 

[Robert Baer]

You've omitted "sinus cavities" and "exhaust headers". ;-)

Ever see that "Blue Man Group" bit where they've got a telescoping piece
of about 6" PVC pipe, and one guy beats on it with drumsticks while another
slides the telescoping part of the pipe in and out? Resonance.

Planetary orbits, electronic orbitals, NMR/MRI, etc, etc, etc...

Cheers!
Rich

One of the more interesting modes (in a waveguide) is the "smoke
ring" mode...apparently not very stable but capable of handling vast
amounts of power.
Now just figgure how to launch energy in such a mode, and....ray gun!

 

[Mark Fergerson]

One of the more interesting modes (in a waveguide) is the "smoke ring"
mode...apparently not very stable but capable of handling vast amounts
of power.

The what mode? Cites?

Now just figgure how to launch energy in such a mode, and....ray gun!

Betcha it can't propagate in free space.


Mark L. Fergerson

 

[hobart Zklfed]

The what mode? Cites?


Betcha it can't propagate in free space.

EZ, no problem, done all the time. But it aint called "smoke ring"
U can use your microwave oven, put a "structure" on it and cook a hotdog at
100 feet.

 

[Robert Baer]

EZ, no problem, done all the time. But it aint called "smoke ring"
U can use your microwave oven, put a "structure" on it and cook a hotdog at
100 feet.

Err...at Stanford Linear Accelerator Center, they wer using higher
power klystrons, and to handle the power without arcing, was to use the
"smoke ring" mode.
That is what they called it because of the shape of the E-H mode.
Argue with them.

 

[Mark Fergerson]

The cooking cavity in a microwave oven is not free space.

Err...at Stanford Linear Accelerator Center, they wer using higher
power klystrons, and to handle the power without arcing, was to use the
"smoke ring" mode.
That is what they called it because of the shape of the E-H mode.
Argue with them.

Cite please? Google gives no relevant returns.


Mark L. Fergerson

 

[Sue...]

Hi all,

What is physical significance of various different modes travelling
inside the waveguide? Why are they so critical, when talking about
confined medium, like waveguide and optic fibre. As it hardly have any
significance in free space!!

Thanks

All the stuff between electrons and protons is free space.
For words and music:
http://www.ee.surrey.ac.uk/Personal/D.Jefferies/wguide.html
....well pics and words anyway.

Treat dielectric and conductive wave guide
just as you treat dielectric and conductive mirrors.
http://en.wikipedia.org/wiki/Waveguide


Sue...