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.
Patent Number: 6,653,987
Date Issued: November 25 2003