Surface wave

From Free net encyclopedia

(Redirected from Groundwave)
Image:Wiki letter w.png Please expand this article.
Please remove this message once the article has been expanded.
Template:TOCright

In physics, a surface wave is, for a mechanical wave, guided along the interface between two differing mediums. A surface wave, for an electromagnetic wave, can be guided along by a refractive index gradient. In radio transmission, a ground wave is a surface wave that propagates close to the surface of the Earth.

Contents

[edit]

Mechanical waves

In seismology, several types of surface waves are encountered. A surface wave, in this mechanical sense, are commonly known as as Rayleigh surface waves. A seismic wave is a wave that travels through the Earth, often as the result of an earthquake or explosion. The Rayleigh waves, also known as "ground rolls", are a type of surface wave associated on the Earth with earthquakes and subterranean movement of magma. Seismic waves are studied by seismologists and measured by a seismograph or seismometer

Surface wave can describe waves propagating over an ocean, even when they are approximated by Airy functions and are more properly called creeping waves. An example is the waves at the surface of water and air, ocean surface waves, or ripples in the sand on the interface of water or wind. Longitudinal and transverse motions of the circles decrease with depth. Another example is internal waves, waves that are transmitted along the interface of two water masses of different densities. .

[edit]

Electrical waves

Ground waves are the propagation of radio waves close to the surface of the Earth. These surface waves are also known as Norton surface waves, Zenneck waves, Sommerfeld waves, or gliding waves.

[edit]

Radio Propagation

Lower frequencies, especially AM broadcasts in the mediumwave (sometimes called "medium frequency") and longwave bands (and other types of radio even below that), travel most efficiently this way. This is because they are more efficiently diffracted by the figure of the Earth due to their low frequencies. Ionospheric reflection is taken into consideration as well. The ionosphere reflects frequencies in a certain band, which often changes due to solar conditions. The Earth has one refractive index and the atmosphere has another, thus constituting an interface that supports the surface wave transmission. This can lead to longitudinal wave propagation. A longitudinal mode of a resonant cavity is a particular standing wave pattern formed by waves confined in the cavity. The longitudinal wave correspond to the wavelengths of which are reinforced by constructive interference after many reflections from the cavity's reflecting surfaces. These can be vertically polarized to allievate short circuiting the electric field through the conductivity of the ground. Since the ground is not a perfect electrical conductor, ground waves are attenuated as they follow the earth’s surface. The refractive indices are subject to spatial and temporal changes.

Most long-distance LF "longwave" radio communication (between 30 and 300 kHz) is a result of groundwave propagation. Mediumwave radio transmissions (frequencies between 300 kHz and 3000 kHz) have the property of following the curvature of the earth (the groundwave) in the majority of occurances. At low frequencies, ground losses are low and become lower at lower frequencies. The VLF and LF frequencies are mostly used for military communications, especially with ships and submarines.

Surface waves have been used in "over-the-horizon" radar. In the development of radio, surface waves were used extensively. Early commercial and professional radio services relied exclusively on long wave, low frequencies and ground-wave propagation. To prevent interference with these services, amateur and experimental transmitters were restricted to the higher (HF) frequencies, felt to be useless since their ground-wave range was limited. Upon discovery of the other propagation modes possible at medium wave and short wave frequencies, the advantages of HF for commercial and military purposes became apparent. Amateur experimentation was then confined only to authorized frequencies in the range.

Mediumwave can reflect off the ionosphere at night (skywave). Because the solar wind "blows" the ionosphere toward the Earth on the day side, and away from it on the night side, this natural radio "mirror" is much closer to the surface during the day. This prevents the high frequency's propagation from being very effective in daylight hours. At night, mediumwave and shortwave transmissions travel better by skywave. Ground waves do not include ionospheric and tropospheric waves.

[edit]

Microwave field theory

Within microwave field theory, the refractive index of many cavities constitute an interface that supports "surface wave transmission". The propagation of surface waves in such structures are used to produce surface waves and behave as a kind of conductor. Surface waves have been studied as part of transmission lines.

Characteristics and utilizations of the electrical surface wave phenomena include:

[edit]

See also

Waves
  • Sky waves, the primary means of HF transmission
People
Other
  • Ground constants, the electrical parameters of earth
  • Near and far field, the radiated field that is within one quarter of a wavelength of the diffracting edge or the antenna and beyond.
  • Skin effect, the tendency of an alternating electric current to distribute itself within a conductor so that the current density near the surface of the conductor is greater than that at its core.
  • Green function, a function used to solve inhomogeneous differential equations subject to boundary conditions.
[edit]

External articles, further readings, and references

[edit]

Web sites

[edit]

Standards and doctrines

[edit]

Books

  • Waldron, Richard Arthur, "Theory of guided electromagnetic waves". London, New York, Van Nostrand Reinhold, 1970. ISBN 0442091672 LCCN 69019848 //r86
  • Weiner, Melvin M., "Monopole antennas" New York, Marcel Dekker, 2003. ISBN 0824704967
  • Wait, J. R., "The Waves in Stratified Media". New York: Pergamon, 1962.
  • Wait, J. R., "Electromagnetic Wave Theory", New York, Harper and Row, 1985.
[edit]

Journals and papers

Zenneck, Sommerfeld, and Norton
  • J. Zenneck, (translators: P. Blanchin, G. Guérard, É. Picot), "Précis de télégraphie sans fil : complément de l'ouvrage : Les oscillations électromagnétiques et la télégraphie sans fil", Paris : Gauthier-Villars, 1911. viii, 385 p. : ill. ; 26 cm. (Tr. Precisions of wireless telegraphy: complement of the work: Electromagnetic oscillations and wireless telegraphy)
  • J. Zenneck, "Uber die Fortpflanzung ebener elektromagnetischer Wellen Mngs einer ebenen Leiterflache und ihre Beziehung zur drahtlosen Telegraphie", Ann. der Phwk, vol. 23, pp. 846-866, Sept. 1907. (Tr. "Over the reproduction of even electromagnetic waves of an even leader-flat and their relationship with the wireless telegraphy" )
  • J. Zenneck, "Eektromagnetische Schwingungen und drahtlose Telegraphie", gart, F. Enke, 1905. xxvii, 1019 p. : ill. ; 24 cm. (Tr. "Electromagnetic oscillations and wireless telegraphy.")
  • J. Zenneck, (translator: A.E. Seelig) "Wireless telegraphy,", New York [etc.] McGraw-Hill Book Company, inc., 1st ed. 1915. xx, 443 p. illus., diagrs. 24 cm. LCCN 15024534 (ed. "Bibliography and notes on theory" p. 408-428.)
  • A. Sommerfeld, "Fortpffanzung elektrodynamischer Wellen an einem zylindnschen Leiter", Ann. der Physik und Chemle, vol. 67, pp. 233–290, Dec 1899. (Tr. Reproduction of electro-dynamic waves at a cylinder leader)
  • A. Sommerfeld, "Uber die Ausbreitlung der Wellen in der drahtlosen Telegraphie", Annalen der Physik, Vol. 28, March, 1909, pp. 665-736. (Tr. Over the Propagation of the waves in the wireless telegraphy)
  • A. Sommerfeld, "Propagation of waves in wireless telegraphy", Ann. Phys., vol. 81, pp. 1367–1153, 1926.
  • K. A. Norton, "The propagation of radio waves over the surface of the earth and in the upper atmosphere", Proc. IRE, vol. 24, pp. 1367–1387, 1936.
  • K. A. Norton, "The calculations of ground wave field intensity over a finitely conducting spherical earth", Proc. IRE, vol. 29, pp. 623–639, 1941.
Wait
  • Wait, J. R., "Lateral Waves and the Pioneering Research of the Late Kenneth A Norton".
  • Wait, J. R., and D. A. Hill, "Excitation of the HF surface wave by vertical and horizontal apertures". Radio Science, 14, 1979, pp 767-780.
  • Wait, J. R., and D. A. Hill, "Excitation of the Zenneck surface by a vertical aperture", Radio Science, 13, 1978, pp. 967-977.
  • Wait, J. R., "A note on surface waves and ground waves", IEEE Transactions on Antennas and Propagation, Nov 1965. Vol. 13, Issue 6, pg 996- 997 ISSN 0096-1973
  • Wait, J. R., "The ancient and modern history of EM ground-wave propagation". IEEE Antennas Propagat. Mag., vol. 40, pp. 7–24, Oct. 1998.
  • Wait, J. R., "Appendix C: On the theory of ground wave propagation over a slightly roughned curved earth", Electromagnetic Probing in Geophysics. Boulder, CO., Golem, 1971, pp. 37–381.
  • Wait, J. R., "Electromagnetic surface waves", Advances in Radio Research, 1, New York, Academic Press, 1964, pp. 157-219.
Others
  • F. J. Zucker, "Surface wave antennas and surface wave excited arrays", Antenna Engineering Handbook, 2nd ed., R. C. Johnson and H. Jasik, Eds. New York: McGraw-Hill, 1984.
  • Hill, D. and J.R Wait, "Excitation of the Zenneck Surface Wave by a Vertical Aperture", Radio Science, Vol. 13, No. 6, November-December, 1978, pp. 969-977.
  • Yu. V. Kistovich, "Possibility of Observing Zenneck Surface Waves in Radiation from a Source with a Small Vertical Aperture", Soviet Physics Technical Physics, Vol. 34, No.4, April, 1989, pp. 391-394.
  • V. I. Baĭbakov, V. N. Datsko, Yu. V. Kistovich, "Experimental discovery of Zenneck's surface electromagnetic waves", Sov Phys Uspekhi, 1989, 32 (4), 378-379.
  • Corum, K. L. and J. F. Corum, "The Zenneck Surface Wave", Nikola Tesla, Lightning Observations, and Stationary Waves, Appendix II. 1994.
  • M. J. King and J. C. Wiltse, "Surface-Wave Propagation on Coated or Uncoated Metal Wires at Millimeter Wavelengths". J. Appl. Phys., vol. 21, pp. 1119-1128; November,
  • Georg Goubau, "Surface waves and their application to transmission lines", J. Appl. Phys., vol. 21, pp. 1119-1128; November,1950.
  • M. J. King and J. C. Wiltse, "Surfare-Wave Propagation on a Dielectric Rod of Elliutic Cross-Section." Electronic Communications, Inc., Tirnonium: kld.. Sci. Rept.'No. 1, AFCKL Contract No. AF 19(601)-5475; August, 1960.
  • T. Kahan and G. Eckart, "On the Electromagnetic Surface Wave of Sommerfeld", Phys. Rev. 76, 406–410 (1949).
[edit]

Other media

  • L.A. Ostrovsky (ed.), "Laboratory modeling and theoretical studies of surface wave modulation by a moving sphere", Environmental Technology Laboratory, U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, Oceanic and Atmospheric Research Laboratories, 2002. OCLC 50325097
fi:Pinta-aalto
Retrieved from "http://www.netipedia.com/index.php/Surface_wave"