Abstract: An antenna including a feed network; four or more helical radiating elements, and four or more impedance matching stubs each coupling a respective radiating element to ground in parallel with the feed network. The shunt stubs provide a reactance in parallel with the radiating elements to rotate the desired frequency locus about a constant admittance curve. Specifically, the shunt stubs rotate the desired frequency locus from a low resistance, capacitive impedance to 50 ohms purely resistive. The length of the stubs can be adjusted to control the inductance.

Abstract: An antenna feed network including a 180° hybrid coupler having a feed port, a 0° port; and a 180° port having an approximately 180° phase difference with the 0° port. A first antenna port is coupled to the 0° port; and a second antenna port is coupled to the 0° port via a respective phased line, the second antenna port having an approximately 90° phase difference with the first antenna port. A third antenna port is coupled to the 180° port; and a fourth antenna port is coupled to the 180° port via a respective phased line, the fourth antenna port having an approximately 90° phase difference with the third antenna port. The feed network can be used to drive antenna elements in phase quadrature. In a preferred embodiment the feed network drives a quadriflar helix antenna.

Abstract: An antenna feed network including a 180° hybrid coupler having a feed port, a 0° port; and a 180° port having an approximately 180° phase difference with the 0° port. A first antenna port is coupled to the 0° port; and a second antenna port is coupled to the 0° port via a respective phased line, the second antenna port having an approximately 90° phase difference with the first antenna port. A third antenna port is coupled to the 180° port; and a fourth antenna port is coupled to the 180° port via a respective phased line, the fourth antenna port having an approximately 90° phase difference with the third antenna port. The feed network can be used to drive antenna elements in phase quadrature. In a preferred embodiment the feed network drives a quadriflar helix antenna.