Abstract: An example system incorporates: an antenna structure having a feed structure and a top radiating element attached to the feed structure; the feed structure having a downwardly pointed, contiguous V-shaped body portion with an upper side extending between first and second inwardly extending sides, the first and second sides meeting at an apex of the V-shaped body portion; the top radiating element being attached to the feed structure along the upper side.

Abstract: Periodic structure assemblies are provided. An example assembly includes: a dielectric layer having a top and a bottom; a first frequency selective layer disposed on the top of the dielectric layer, the first frequency selective layer having a plurality of electrically conductive elements arranged as a first periodic structure; and a second frequency selective layer disposed on the bottom of the dielectric layer, the second frequency selective layer having a plurality of electrically conductive elements arranged as a second periodic structure. Another periodic structure assembly includes: a substrate; and an array of periodic elements defined by a contiguous trace of conductive material supported by the substrate, each of the periodic elements exhibiting side walls, with each of the side walls having an inwardly extending protrusion.

Abstract: Periodic structure assemblies are provided. An example assembly includes: a dielectric layer having a top and a bottom; a first frequency selective layer disposed on the top of the dielectric layer, the first frequency selective layer having a plurality of electrically conductive elements arranged as a first periodic structure; and a second frequency selective layer disposed on the bottom of the dielectric layer, the second frequency selective layer having a plurality of electrically conductive elements arranged as a second periodic structure. Another periodic structure assembly includes: a substrate; and an array of periodic elements defined by a contiguous trace of conductive material supported by the substrate, each of the periodic elements exhibiting side walls, with each of the side walls having an inwardly extending protrusion.

Abstract: Cross-dipole antenna configurations are provided. A representative cross-dipole antenna includes: a feed structure; a first antenna half, electrically connected to the feed structure, having a first conductive arm and a second conductive arm; a second antenna half, electrically connected to the feed structure, having a third conductive arm and a fourth conductive arm; wherein the first conductive arm, the second conductive arm, the third conductive arm, and the fourth conductive arm, are spaced apart from each other by about 90 degrees such that a proximal end of each of the arms is arranged near a center point and each of the arms extends generally outward to a distal end; wherein the first antenna half and the second antenna half exhibit a gap therebetween adjacent the proximal end of each of the arms.

Abstract: A choke ring apparatus for attenuation of electromagnetic waves in a mobile platform fuselage includes a ground plane mounted on a surface of the fuselage. The choke ring has an axial circular window and a series of concentric circular ring segments on the ground plane arranged coaxially about the axis of the window. The circular ring segments extend from the ground plane. The ring segments defining at least one groove therebetween. The ring segments have a flat ridge at the edge, and each groove has a depth defined by a pair of adjacent ring segments. The width of the flat ridge surfaces and a width of the groove between adjacent ring segments are approximately equal. The depth of the groove is determined based on a predetermined resonant frequency, such that the choke ring apparatus selectively attenuates electromagnetic waves in a region of the resonant frequency when propagating through the window.

Abstract: An antenna system comprises a parasitic element, which is an electrically tuned structural element, installed between antennas to reduce or eliminate antenna-to-antenna coupled electromagnetic interference by emitting destructive interference in the direction from one antenna to another antenna. The antenna system comprises a first antenna operating at a first wavelength, a second antenna operating at a second wavelength, and a parasitic element located between the first antenna and the second antenna for reducing the amplitude of signals from the first antenna that would otherwise create electromagnetic interference in a receiver connected to the second antenna. The parasitic element is typically spaced from the first antenna by a distance substantially equal to one quarter of the first wavelength. The parasitic element generally has a height that is greater than the height of the first antenna.

Abstract: A choke ring apparatus for attenuation of electromagnetic waves in a mobile platform fuselage includes a ground plane mounted on a surface of the fuselage. The choke ring has an axial circular window and a series of concentric circular ring segments on the ground plane arranged coaxially about the axis of the window. The circular ring segments extend from the ground plane. The ring segments defining at least one groove therebetween. The ring segments have a flat ridge at the edge, and each groove has a depth defined by a pair of adjacent ring segments. The width of the flat ridge surfaces and a width of the groove between adjacent ring segments are approximately equal. The depth of the groove is determined based on a predetermined resonant frequency, such that the choke ring apparatus selectively attenuates electromagnetic waves in a region of the resonant frequency when propagating through the window.

Abstract: An antenna system comprises a parasitic element, which is an electrically tuned structural element, installed between antennas to reduce or eliminate antenna-to-antenna coupled electromagnetic interference by emitting destructive interference in the direction from one antenna to another antenna. The antenna system comprises a first antenna operating at a first wavelength, a second antenna operating at a second wavelength, and a parasitic element located between the first antenna and the second antenna for reducing the amplitude of signals from the first antenna that would otherwise create electromagnetic interference in a receiver connected to the second antenna. The parasitic element is typically spaced from the first antenna by a distance substantially equal to one quarter of the first wavelength. The parasitic element generally has a height that is greater than the height of the first antenna.

Abstract: A choke ring apparatus for attenuation of electromagnetic waves in a mobile platform fuselage includes a ground plane mounted on a surface of the fuselage. The choke ring has an axial circular window and a series of concentric circular ring segments on the ground plane arranged coaxially about the axis of the window. The circular ring segments extend from the ground plane. The ring segments defining at least one groove therebetween. The ring segments have a flat ridge at the edge, and each groove has a depth defined by a pair of adjacent ring segments. The width of the flat ridge surfaces and a width of the groove between adjacent ring segments are approximately equal. The depth of the groove is determined based on a predetermined resonant frequency, such that the choke ring apparatus selectively attenuates electromagnetic waves in a region of the resonant frequency when propagating through the window.

Abstract: An antenna system comprises a parasitic element, which is an electrically tuned structural element, installed between antennas to reduce or eliminate antenna-to-antenna coupled electromagnetic interference by emitting destructive interference in the direction from one antenna to another antenna. The antenna system comprises a first antenna operating at a first wavelength, a second antenna operating at a second wavelength, and a parasitic element located between the first antenna and the second antenna for reducing the amplitude of signals from the first antenna that would otherwise create electromagnetic interference in a receiver connected to the second antenna. The parasitic element is typically spaced from the first antenna by a distance substantially equal to one quarter of the first wavelength. The parasitic element generally has a height that is greater than the height of the first antenna.

Abstract: A choke ring apparatus for attenuation of electromagnetic waves in a mobile platform fuselage includes a ground plane mounted on a surface of the fuselage. The choke ring has an axial circular window and a series of concentric circular ring segments on the ground plane arranged coaxially about the axis of the window. The circular ring segments extend from the ground plane. The ring segments defining at least one groove therebetween. The ring segments have a flat ridge at the edge, and each groove has a depth defined by a pair of adjacent ring segments. The width of the flat ridge surfaces and a width of the groove between adjacent ring segments are approximately equal. The depth of the groove is determined based on a predetermined resonant frequency, such that the choke ring apparatus selectively attenuates electromagnetic waves in a region of the resonant frequency when propagating through the window.

Abstract: An antenna system comprises a parasitic element, which is an electrically tuned structural element, installed between antennas to reduce or eliminate antenna-to-antenna coupled electromagnetic interference by emitting destructive interference in the direction from one antenna to another antenna. The antenna system comprises a first antenna operating at a first wavelength, a second antenna operating at a second wavelength, and a parasitic element located between the first antenna and the second antenna for reducing the amplitude of signals from the first antenna that would otherwise create electromagnetic interference in a receiver connected to the second antenna. The parasitic element is typically spaced from the first antenna by a distance substantially equal to one quarter of the first wavelength. The parasitic element generally has a height that is greater than the height of the first antenna.