Waveguide

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Contents 1 History 2 Physical structure 3 Optics 4 See also 5 External links 6 References

History

Waveguides are used in physics and microwave telecomunications to propagate electromagnetic waves or radio frequencies in hollow metallic tubes. The first waveguide was proposed by J. J. Thomson in 1893 and experimentally verified by O. J. Lodge in 1894; the mathematical analysis of the propagating modes within a hollow metal cylinder was first performed by Lord Rayleigh in 1897. (McLachan, 1947.)

• Sources: in part from Federal Standard 1037C and from MIL-STD-188, and ATIS

Physical structure

In the microwave region of the electromagnetic spectrum, a waveguide normally consists of a hollow metallic conductor. In some waveguides, there may be a positive pressure internally present or a better solution to detect RF leakage of a waveguide is to have vacuum. This way the waveguide may be monitored for leakage.

A slotted waveguide is generally used for radar and other similar applications. The waveguide structure has the capability of confining and supporting the energy of an electromagnetic wave to a specific relatively narrow and controllable path. Waveguides are altered to suit the needs of the medium communicated, such as microwave guides, and coaxial cables. In physics and electronics every Klystron has a waveguide to process and propagating the transmitted RF output.

Optics

In digital computing, the term waveguide can also be used for data buffers used as delay lines that simulate physical waveguide behavior, such as in digital waveguide synthesis.

Waveguide propagation modes depend on the operating wavelength and polarization and the shape and size of the guide. In hollow metallic waveguides, the fundamental modes are the transverse electric TE_1,0 mode for rectangular and TE_1,1 for circular waveguides, seen here in cross-section:

A dielectric waveguide is a waveguide that consists of a dielectric material surrounded by another dielectric material, such as air, glass, or plastic, with a lower refractive index. An example of a dielectric waveguide is an optical fiber. Paradoxically, a metallic waveguide filled with a dielectric material is not a dielectric waveguide.

A closed waveguide is an electromagnetic waveguide (a) that is tubular, usually with a circular or rectangular cross section, (b) that has electrically conducting walls, (c) that may be hollow or filled with a dielectric material, (d) that can support a large number of discrete propagating modes, though only a few may be practical, (e) in which each discrete mode defines the propagation constant for that mode, (f) in which the field at any point is describable in terms of the supported modes, (g) in which there is no radiation field, and (h) in which discontinuities and bends cause mode conversion but not radiation.

See also

• Angular misalignment loss
• Cutoff wavelength
• Dielectric constant
• Electromagnetic radiation
• Feedhorn
• Filled cable
• Horn (telecommunications)
• Leaky mode

• List of telecommunications transmission terms
• List of antenna terms
• List of fiber optic terms
• Klystron tube
• Radiation mode
• Radio wave
• Radio propagation
• Transmission medium

External links

• Waveguides in particle accelerators incorporating Klystons

References

• J. J. Thomson, Recent Researches (1893). O. J. Lodge, Proc. Roy. Inst. 14, p. 321 (1894). Lord Rayleigh, Phil. Mag. 43, p. 125 (1897). See also N. W. McLachlan, Theory and Applications of Mathieu Functions, p. 8 (1947) (reprinted by Dover: New York, 1964).fr:Guide d'onde

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