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.