Goubou line
Encyclopedia
A Goubau line or G-line for short, is a single wire transmission line
intended for use at UHF and microwave
wavelengths.
A G-line is a type of 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.
Note that the Goubau-Line are not exclusively coupled to 3 dimensional horn antennas, and can be used at other frequencies besides UHF and Microwave. Waves can be "launched" from planar structures like tapered Coplanar Waveguides (CPW) at much higher frequencies such as the Terahertz Band. The dimension of the single metallic conductor is then typically 1µm.
The phenomena behind G-line operation is the one-dimensional case of electromagnetic surface waves. The two-dimensional case appears in over-the-horizon radar
and in radio ground waves as employed in the GWEN
system.
Transmission line
In communications and electronic engineering, a transmission line is a specialized cable designed to carry alternating current of radio frequency, that is, currents with a frequency high enough that its wave nature must be taken into account...
intended for use at UHF and microwave
Microwave
Microwaves, a subset of radio waves, have wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz and 300 GHz. This broad definition includes both UHF and EHF , and various sources use different boundaries...
wavelengths.
Description
The Goubau line itself consists of a single conductor coated with dielectric material. 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.A G-line is a type of waveguide
Waveguide (electromagnetism)
In electromagnetics and communications engineering, the term waveguide may refer to any linear structure that conveys electromagnetic waves between its endpoints. However, the original and most common meaning is a hollow metal pipe used to carry radio waves...
, 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.
Note that the Goubau-Line are not exclusively coupled to 3 dimensional horn antennas, and can be used at other frequencies besides UHF and Microwave. Waves can be "launched" from planar structures like tapered Coplanar Waveguides (CPW) at much higher frequencies such as the Terahertz Band. The dimension of the single metallic conductor is then typically 1µm.
The phenomena behind G-line operation is the one-dimensional case of electromagnetic surface waves. The two-dimensional case appears in over-the-horizon radar
Over-the-horizon radar
Over-the-horizon radar, or OTH , is a design concept for radar systems to allow them to detect targets at very long ranges, typically up to thousands of kilometers...
and in radio ground waves as employed in the GWEN
Ground Wave Emergency Network
The Ground Wave Emergency Network was a command and control communications system intended for use by the United States government to facilitate military communications before, during and after a nuclear war...
system.
See also
- Surface waveSurface waveIn physics, a surface wave is 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...
- Single-wire transmission lineSingle-wire transmission lineA single-wire transmission line is a method of supplying electrical power through a single electrical conductor.-History:In 1729, the English physicist Stephen Gray noticed the phenomenon of electrical conductivity...
- Radio frequency power transmissionRadio frequency power transmissionRadio frequency power transmission is the transmission of the output power of a transmitter to an antenna. When the antenna is not situated close to the transmitter, special transmission lines are required....