A waveguide is a special form of transmission line
consisting of a hollow, metal tube.
Source: http://www.allaboutcircuits.com/
Wave guides conduct microwave energy at lower loss than
coaxial cables.
Only for signals of extremely high frequency, the wavelength
approaches the cross-sectional dimensions of the waveguide.
Below such frequencies, waveguides are useless as electrical
transmission lines.
Waveguides may be thought of as conduits for electromagnetic
energy, the waveguide itself acting as nothing more than a “director” of the
energy rather than as a signal conductor in the normal sense of the word.
All transmission lines function as conduits of
electromagnetic energy when transporting pulses or high-frequency waves, directing
the waves as the banks of a river direct a tidal wave.
Waveguides are single-conductor elements; the propagation of
electrical energy down a waveguide is of a very different nature than the
propagation of electrical energy down a two-conductor transmission line.
Standing Wave
Formation:
A standing wave pattern is a vibration pattern created
within a medium when the vibrational frequency of the source causes reflected
waves from one end of the medium to interfere with incident waves from the source.
Important part of the condition for this constructive
interference for stretched strings is the fact that the waves change phase upon
reflection from a fixed end.
Only created within the medium at specific frequencies of
vibration.
These standing wave modes arise from the combination of
reflection and interference such that the reflected waves interfere
constructively with the incident waves.
Source: http://hyperphysics.phy-astr.gsu.edu/
Standing wave used in medicine.
Have advantages at low energies.
However, it is insufficient because it tries to combine two
components that are out of phase.
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