Description Goubau line

1955 article on goubau feedline uhf television antennas showing line , cone launchers.

the goubau line consists of single wire conductor coated dielectric material. coupling , g-line done conical metal launchers or catchers , narrow ends connected example shield of coaxial feed line, , transmission line passing through hole in conical tips. advantage of goubau line can have lower attenuation due dielectric losses @ high frequencies other types of transmission line. parallel line (twin lead) , coaxial cable, used carry lower frequency radio signals, have high losses @ upper end of uhf band, , useless distances on 100 feet (33 meters). goubau lines can serve low loss antenna feedlines @ these frequencies, microwave frequencies waveguide must used.

a g-line type of waveguide, rather wire in electric circuit. g-line functions slowing propagation velocity of em waves below free-space velocity, causing wavefronts bend inwards towards conductor, keeps waves entrained. bends of large radius tolerated, sharp bend in single wire cause line radiate , lose energy space. in theory dielectric coating requirement, slows wave , focuses along wire. users note in practice finite conductivity of metals may produce similar effect, , bare g-line can entrain propagating wave.

other structures besides horns have been used couple radio waves , out of goubau lines; waves can launched planar structures tapered coplanar waveguides @ higher frequencies, terahertz band. dimension of single metallic conductor typically 1 µm.

the goubau line conducts energy via one-dimensional electromagnetic surface waves, analogous two-dimensional surface waves called ground waves carry signal mf broadcasting stations home radios. ability of surface waves bend , follow contour of conductor explains why radio stations can received on far side of hills, , how over-the-horizon radar works.