Patent ID: 7429957

Claim:
A buoyant cable antenna for use with an underwater vehicle comprising: a coaxial feed line having a first end and a second end, said first end being joined to said underwater vehicle, wherein said coaxial feed line serves as a transmission line; an exposed braid of coaxial feed line having a first end and a second end, wherein said first end of said exposed braid of coaxial feed line is joined to the second end of the coaxial feed line; an antenna element that is positively buoyant in a body of water, having a first end and a second end wherein said first end of said antenna element is joined to said second end of said exposed braid of coaxial feed line, said antenna element further comprising: a straight wire of conducting metal of uniform diameter along its length; a cylindrical sheath of dielectric material surrounding said straight wire, wherein said cylindrical sheath of dielectric material serves to insulate said straight wire; a cylindrical sheath of a double-negative meta-material surrounding said cylindrical sheath of dielectric material, wherein said cylindrical sheath of double negative meta-material is a non-conducting material whose dielectric constant and relative permeability are both negative numbers over a specific frequency range; and a shorting cap joined to the second end of said antenna element, wherein said shorting cap is a solid metallic structure that connects electrically to the center conductor of the antenna and conforms to the overall diameter of the antenna; wherein the cylindrical sheath of double-negative meta-material has a specific negative permeability value directly related to a desired critical frequency such that the inductance of said straight wire is reduced to zero at said desired critical frequency, which in turn creates a traveling wave of current along said straight wire.