| [Edit]
In physics, a surface wave can refer to a mechanical wave that propagates along the interface between differing media, usually two fluids with different densities. A surface wave can also be an electromagnetic wave guided by a refractive index gradient. In radio transmission, a ground wave is a surface wave that propagates close to the surface of the Earth.
top
Mechanical waves
In seismology, several types of surface waves are encountered. Surface waves, in this mechanical sense, are commonly known as either Love waves or Rayleigh waves. A seismic wave is a wave that travels through the Earth, often as the result of an earthquake or explosion. Love waves have transverse motion (movement is perpendicular to the direction of travel, like light waves), whereas Rayleigh waves have both longitudinal (movement parallel to the direction of travel, like sound waves) and transverse motion. Seismic waves are studied by seismologists and measured by a seismograph or seismometer. Surface waves span a wide frequency range, and the period of waves that are most damaging is usually 10 seconds or longer. Surface waves can travel around the globe many times from the strongest earthquakes.
Surface wave can describe waves propagating over an ocean, even when they are approximated by Airy functions and are more properly called creeping waves. Examples are the waves at the surface of water and air (ocean surface waves), or ripples in the sand at the interface with water or air. Another example is internal waves, which can be transmitted along the interface of two water masses of different densities.
top
Electromagnetic waves
Ground waves refer to the propagation of radio waves close to or at the surface of the Earth. These surface waves are also known as Norton surface waves, Zenneck waves, Sommerfeld waves, or gliding waves.
top
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 efficiently as a surface wave. 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.
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.
Conductivity of the surface affects the propagation of ground waves, with more conductive surfaces such as water providing better propogation. allievate Increase of the conductivity in the surface results in less dissipation. The refractive indices are subject to spatial and temporal changes. Since the ground is not a perfect electrical conductor, ground waves are attenuated as they follow the earth’s surface.
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 occurrences. 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.
top
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:
The field components of the wave diminish with distance from the interface.
Optical energy is not converted from the surface wave field to another form of energy and the wave does not have a component directed normal to the interface surface.
top
See also
Waves
Sky waves, the primary means of HF transmission
Gravity waves, occurs at certain natural interfaces (e.g. the atmosphere and ocean)
People
Other
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.
top
Citations
top
Web sites
Eric W. Weisstein, et. al., "Surface Wave", Eric Weisstein's World of Physics, 2006.
top
Patents
, "Launching and receiving of surface waves". George J. E. Goubau.
top
Standards and doctrines
"Surface wave". Telecom Glossary 2000, ATIS Committee T1A1, Performance and Signal Processing, T1.523-2001.
top
Books
Waldron, Richard Arthur, "Theory of guided electromagnetic waves". London, New York, Van Nostrand Reinhold, 1970. ISBN 0-442-09167-2 LCCN 69019848 //r86
Weiner, Melvin M., "Monopole antennas" New York, Marcel Dekker, 2003. ISBN 0-8247-0496-7
Wait, J. R., "The Waves in Stratified Media". New York: Pergamon, 1962.
Wait, J. R., "Electromagnetic Wave Theory", New York, Harper and Row, 1985.
Budden, K. G., " The propagation of radio waves the theory of radio waves of low power in the ionosphere and magnetosphere ". Cambridge (Cambridgeshire); New York Cambridge University Press, 1985. ISBN 0-521-25461-2 LCCN 84028498
Budden, K. G., "Radio waves in the ionosphere; the mathematical theory of the reflection of radio waves from stratified ionised layers". Cambridge, Eng., University Press, 1961. LCCN 61016040 /L/r85
Budden, K. G., "The wave-guide mode theory of wave propagation". London, Logos Press; Englewood Cliffs, N.J., Prentice-Hall, c1961. LCCN 62002870 /L
top
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).
top
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
|
|
