Abstract: The antenna includes four elements excited with equal amplitudes but with a relative phase difference of 0°, ?90°, ?180°, and ?270°. Each element includes a vertical and horizontal portion. An RF trap filter is located within the horizontal portion so that the antenna provides good gain coverage at all three frequency bands of a modernized global positioning system.

Abstract: The antenna includes four elements excited with equal amplitudes but with a relative phase difference of 0°, −90°, −180°, and −270°. Each element includes a vertical and horizontal portion. An RF trap filter is located within the horizontal portion so that the antenna provides good gain coverage at all three frequency bands of a modernized global positioning system.

Abstract: Single and dual frequency band spatial null steering antenna arrays are disclosed, comprised of primary resonant quadrifilar helix antennas and auxiliary resonant patch antennas, which comprise stacked patches in the dual-band embodiments. Several feed networks are described for producing, preferably, circularly polarized radiation in satellite frequency bands (e.g., L1 and L2) with pattern nulls steerable to desired elevation angles. Various top and bottom-fed quadrifilar helix antennas configurations are also described.

Abstract: Single and dual frequency band spatial null steering antenna arrays are disclosed, comprised of primary resonant quadrifilar helix antennas and auxiliary resonant patch antennas, which comprise stacked patches in the dual-band embodiments. Several feed networks are described for producing, preferably, circularly polarized radiation in satellite frequency bands (e.g., L1 and L2) with pattern nulls steerable to desired elevation angles. Various top and bottom-fed quadrifilar helix antennas configurations are also described.

Abstract: Dual-band quadrifilar helix antennas, comprising four radiating elements arranged helically to define a cylinder of constant radius, each radiating element having an upper portion and a lower portion and a gap there between, each upper portion having an open end, and each lower portion having a feed point for receiving feed signals in phase quadrature. Disposed within each gap and electrically connected to each upper and lower portion is a corresponding parallel LC circuit configured to have a first impedance at a first frequency, and a second impedance greater than the first impedance, at a second frequency. Alternative embodiments include structures with ground planes and top-fed helices without ground planes.