Editing Goubau line

{{short description|Single wire transmission line used to conduct radio waves at UHF and microwave frequencies}}
A '''Goubau line''' or '''Sommerfeld–Goubau line''',<ref name="Yeh">{{cite book
 | last1 = Yeh
 | first1 = C. 
 | last2 = Shimabukuro
 | first2 = F.
 | title = The Essence of Dielectric Waveguides
 | publisher = Springer Science & Business Media
 | date   = 2000
 | url    = https://books.google.com/books?id=1WWjsqKwq6UC&q=sommerfeld-goubau&pg=PA152
 | isbn   = 0387497994
 }}</ref> or G-line for short, is a [[single-wire transmission line]] used to conduct [[radio wave]]s at [[Ultrahigh frequency|UHF]] and [[microwave]] [[frequencies]].<ref name="Straw" /><ref name="Lieberman">{{cite journal
  | last = Lieberman
  | first = Leonard
  | title = The G-Line Antenna Lead-In
  | journal = Radio and Television News
  | volume = 53
  | issue = 4
  | pages = 124–125
  | date = April 1955
  | url = http://www.americanradiohistory.com/Archive-Radio-News/50s/Radio-News-1955-04-R.pdf
  | access-date = September 14, 2014}}</ref><ref name="Griffith">{{cite book
 | last1  = Griffith
 | first1 = B. Whitfield Jr.
 | title  = Radio-electronic Transmission Fundamentals
 | publisher = SciTech Publishing
 | date   = 2000
 | pages  = 307–308
 | url    = https://books.google.com/books?id=m5DIroWLw2EC&q=goubau&pg=PA307
 | isbn   = 1884932134
 }}</ref>  The dielectric coated transmission line was invented by F. Harms<ref name="Harms">{{cite journal
  | last = Harms
  | first = F.
  | title = Elektromagnetische Wellen an einem Draht mit isolierender zylindrischer Hulle
  | trans-title = Electromagnetic waves on a wire with a cylindrical insulating sheath
  | journal = Annalen der Physik
  | volume = 23
  | issue = 6
  | pages = 44–60
  | date = 1907
  | url = https://zenodo.org/record/1424093
  | doi = 10.1002/andp.19073280603
  | bibcode = 1907AnP...328...44H
  }} cited in [https://accelconf.web.cern.ch/accelconf/BIW2012/papers/tupg007.pdf   Stulle, Bergoz 2012 ''The Goubau line'', p.148] {{Webarchive|url=https://web.archive.org/web/20141124220553/http://accelconf.web.cern.ch/AccelConf/BIW2012/papers/tupg007.pdf |date=2014-11-24 }}</ref> in 1907 and George J. E. Goubau<ref name="Goubau">{{cite journal
  | last = Goubau
  | first = G.
  | title = Surface waves and their application to transmission lines
  | journal = Journal of Applied Physics
  | volume = 21
  | pages = 1119–1128
  | date = 1950
  | issue = 11
 | doi = 10.1063/1.1699553
 | bibcode = 1950JAP....21.1119G
 }} cited in [https://accelconf.web.cern.ch/accelconf/BIW2012/papers/tupg007.pdf   Stulle, Bergoz 2012 ''The Goubau line'', p.148] {{Webarchive|url=https://web.archive.org/web/20141124220553/http://accelconf.web.cern.ch/AccelConf/BIW2012/papers/tupg007.pdf |date=2014-11-24 }}</ref> in 1950, based on work on surface waves on wires from 1899 by [[Arnold Sommerfeld]].<ref name="Sommerfeld">{{cite journal
  | last = Sommerfeld
  | first = A.
  | title = Ueber die Fortpflanzung elektrodynamischer Wellen längs eines Drahtes
  | journal = Annalen der Physik und Chemie
  | volume = 67
  | issue = 2
  | pages = 233–290
  | date = 1899
  | doi = 10.1002/andp.18993030202
  | bibcode = 1899AnP...303..233S
  | url = https://zenodo.org/record/1423956
  }} cited in [https://accelconf.web.cern.ch/accelconf/BIW2012/papers/tupg007.pdf   Stulle, Bergoz 2012 ''The Goubau line'', p.148] {{Webarchive|url=https://web.archive.org/web/20141124220553/http://accelconf.web.cern.ch/AccelConf/BIW2012/papers/tupg007.pdf |date=2014-11-24 }}</ref><ref name="Stulle">{{cite book
  | last1 = Stulle
  | first1 = F.
  | last2 = Bergoz
  | first2 = J.
  | chapter = The Goubau line - Surface waves for bench testing of beam instrumentation at high frequencies
  | title = BIW2012: 15th Beam Instrumentation Workshop
  | pages = 146–148
  | publisher = Joint Accelerator Conferences Website
  | date = April 15–19, 2012
  | location = Newport News, Virginia
  | url = https://accelconf.web.cern.ch/accelconf/BIW2012/papers/tupg007.pdf
  | isbn = 978-3-95450-121-2
  | access-date = September 15, 2014
  | archive-date = November 24, 2014
  | archive-url = https://web.archive.org/web/20141124220553/http://accelconf.web.cern.ch/AccelConf/BIW2012/papers/tupg007.pdf
  | url-status = dead
  }}</ref>  It is used as a [[feedline]] at [[Ultrahigh frequency|UHF]] to link high frequency [[transmitter]]s and [[radio receiver|receivers]] to their [[antenna (radio)|antenna]]s,<ref name="Straw" /><ref name="Lieberman" /> and in scientific research.<ref name="Stulle" />

[[File:Goubau.gif|Illustration from Goubau's patent showing the conductor and launchers|thumb|350 px]]

==Description==
[[Image:Goubau line antenna lead-in Radio & Television News April 1955.jpg|thumb|upright=1.4|1955 article on Goubau [[feedline]] for [[Ultrahigh frequency|UHF]] [[television antenna]]s<ref name="Lieberman" /> showing line and cone launchers]]

The ''Goubau line'' itself consists of a single wire conductor coated with [[dielectric]] material.<ref name="Straw">{{cite book
 | last1  = Straw
 | first1 = R. Dean, Ed.
 | title  = The ARRL Antenna Book, 19th Ed.
 | date   = 2000
 | pages  = 18.2–18.3
 | isbn   = 0872598179
 }}</ref>  Coupling to and from the G-line is done with conical metal "launchers" or "catchers", with their narrow ends connected for example to the shield of [[coaxial]] feed line, and with the transmission line passing through a hole in the conical tips.<ref name="Straw" />  An advantage of the Goubau line is that it can have lower attenuation due to dielectric losses at high frequencies than other types of [[transmission line]].  Parallel line ([[twin lead]]) and [[coaxial cable]], which are used to carry lower frequency radio signals, have high losses at the upper end of the [[Ultrahigh frequency|UHF]] band, and are almost useless for distances over 100 feet (33 meters).<ref name="Straw" />  Goubau lines can serve as low loss antenna [[feedline]]s at these frequencies, up to microwave frequencies where a [[waveguide]] must be used."<ref name="Straw" />

A G-line is a type of [[waveguide (electromagnetism)|waveguide]], rather than a wire in an [[electric circuit]].  The G-line functions by slowing the propagation velocity of EM waves below the free-space velocity, causing the wavefronts to slightly bend inwards towards the conductor, which keeps the waves entrained.   Bends of large radius are tolerated, but too sharp a bend in the single wire will cause the line to radiate and lose energy into space.   In theory the dielectric coating is a requirement, it slows the wave and focuses it along the wire.  But some users note that in practice the finite conductivity of metals may produce a similar effect, and a bare G-line can entrain a propagating wave.

Other structures besides horns have been used to couple radio waves into and out of Goubau lines; waves can be "launched" from planar structures like tapered [[coplanar waveguide]]s at much higher frequencies, into the [[Terahertz radiation|terahertz]] band. The dimension of the single metallic conductor is then typically 1&nbsp;μm.
<ref>
''T. Akalin, “High Resolution Biosensor based on Surface Wave Transmission Lines at THz Frequencies”, 35th European Microwave Conf., 3-7 Oct. 2005, Paris, France'' and

''T. Akalin, "Single-wire transmission lines at terahertz frequencies", IEEE Transactions on Microwave Theory and Techniques (IEEE-MTT), Volume 54, Issue 6, June 2006 Page(s): 2762 - 2767''
</ref>

The Goubau line conducts energy via one-dimensional [[surface waves#Electromagnetic waves|electromagnetic surface waves]], analogous to the two-dimensional surface waves called [[ground wave]]s that carry the signal from [[medium frequency|MF]] [[AM broadcasting]] stations to home AM radios.  The ability of surface waves to bend and follow the contour of a conductor explains why AM radio stations can be received on the far side of hills, and how [[over-the-horizon radar]] works.

==See also==
* [[Surface wave]]
* [[Surface plasmon polariton]]
* [[Radio frequency power transmission]]

==Patents==
* {{US patent|2685068}}, "''Surface wave transmission line''". [[George J. E. Goubau]]
* {{US patent|2921277}}, "''Launching and receiving of surface waves''". George J. E. Goubau.

==References==
{{reflist}}

[[Category:Microwave technology]]
[[Category:Surface waves]]