초록 ▼

A buoyant cable antenna element is taught that employs a specific double-negative meta-material sheath with a negative permeability. The double-negative meta-material sheath is disposed over the insulated wire portion of the buoyant cable antenna element. The double-negative meta-material sheath ena

A buoyant cable antenna element is taught that employs a specific double-negative meta-material sheath with a negative permeability. The double-negative meta-material sheath is disposed over the insulated wire portion of the buoyant cable antenna element. The double-negative meta-material sheath enables a deliberate reduction in the antenna wire inductance to a zero value at a desired critical frequency. Reducing the antenna wire inductance to zero creates a traveling wave structure antenna having enhanced bandwidth.

대표청구항 ▼

What is claimed is: 1. 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 fe

What is claimed is: 1. 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. 2. The apparatus of claim 1 wherein there are no air gaps between the straight wire and the cylindrical sheath of dielectric material and the cylindrical sheath of double-negative meta-material. 3. The apparatus of claim 1 wherein the per-unit length inductance of said straight wire can be expressed as: wherein a, b, and c, are the outer radii of said straight wire, the cylindrical sheath of dielectric material and the cylindrical sheath of double-negative (DNG) meta-material, respectively, μ2 is the permeability of the cylindrical sheath of double-negative meta-material, μ0 is the permeability of free space, σocean is the electrical conductivity of the ocean, and γEuler is Euler's constant (approximately 1.781), wherein the last term of said equation decreases with increasing frequency such that when μ2 is negative then there can exist a critical frequency at which said inductance L of said straight wire is zero.