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Elementary Question of cutoff frequency in waveguide - RF Cafe Forums
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rifle
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Post subject: Elementary Question of cutoff frequency in waveguide
Posted: Fri Jun 22, 2007 10:14 pm
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Joined: Sun Jun 17, 2007
9:05 pm Posts: 1 |
Got a little confused by the cutoff phenomena happened
in waveguides, need your help please. For example
a rectangular waveguide has its first two cutoff
freq to be TE10 ~ 6.56GHz and TE20 ~ 13.12GHz, and
I feed in a wave of freq 14GHz (does this wave have
to be a TE or TM wave so that it can actually propagate?)
, then there should have at least two modes(TE10&TE20)
co-exist inside the waveguide right? and, although
the wave bears two different modes for propagation,
it still maintains its own frequency, i.e. 14GHz,
right? if I'm right so far, then the thing bothers
me a lot is that, how can this monochromatic wave
having two different wavelengths inside the waveguide?
Thank you so much for your patient explanation!
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Chaicustard |
Post subject:
Posted: Mon Sep 24, 2007 8:18 am
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Joined: Mon Sep 24, 2007
1:01 am Posts: 1 Location: Adelaide, Australia
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Simply put, different modes can take slightly different
times to traverse the guide. Its the same phenomenon
that leads to pulse spreading in multimode optical
fiber.
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nubbage |
Post subject:
Posted: Fri Oct 05, 2007 7:22 am
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General |
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Joined: Fri Feb 17, 2006
12:07 pm Posts: 218 Location: London UK
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Another related point is that although the over-sized
guide can support both modes, initially only the
14GHz TE10 mode would be excited by the launcher.
Further down the guide, the mode might then de-generate
into higher modes, simply because the geometry satisfies
Maxwell's equation solutions and so they can be
supported.
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Posted 11/12/2012
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