Ground plane interference elimination by passive element
First Claim
1. In a system utilizing a phased array antenna on the ground for communication with a satellite, a method of reducing multipath disturbances in the beam of said antenna due to ground reflections comprising the steps of intercepting in a waveguide section a portion of the energy radiated by said antenna in the direction of the ground, and reradiating it out of phase with the portion of energy not intercepted, thereby decreasing the antenna power at low elevation angles where interfering multipath radiation of said antenna occurs.
2 Assignments
0 Petitions
Accused Products
Abstract
The radiation pattern of a beam at elevation angles near the horizon is improved for phased array antennas by control of the radiation field intensity near the horizon to reduce multipath disturbances, and to improve the axial ratio of a circularly polarized phased array antenna. This is accomplished by placing a parasitic phase shifting element directly below the antenna beam axis. The waveguide section is designed to produce a phase shift in the portion of antenna radiation energy passing through it to cancel some of the radiation energy in the direction of the horizon. The spacing of the waveguide section in front of the antenna is determined empirically for optimum results, i.e., for reduction of beam power below about 20° without affecting beam power at high elevation angles.
17 Citations
9 Claims
- 1. In a system utilizing a phased array antenna on the ground for communication with a satellite, a method of reducing multipath disturbances in the beam of said antenna due to ground reflections comprising the steps of intercepting in a waveguide section a portion of the energy radiated by said antenna in the direction of the ground, and reradiating it out of phase with the portion of energy not intercepted, thereby decreasing the antenna power at low elevation angles where interfering multipath radiation of said antenna occurs.
-
3. A system for communication with a satellite utilizing a circulating polarized phased array antenna on the ground, a method of improving the axial ratio of said circularly polarized antenna at elevation angles near the horizon comprising the steps of intercepting in a waveguide section a portion of the energy radiated in the direction of the horizon, and reradiating it out of phase with the portion of energy not intercepted, thereby reducing the antenna power in the direction of the horizon to improve the axial ratio of the circularly polarized antenna.
-
4. In a mobile radio communication system utilizing a geostationary satellite link and a phased array antenna mounted on a mobile ground plane, means for reducing multipath disturbances due to surrounding ground reflections from said antenna having a beam with its axis at an elevation angle between 20°
- and 60°
, comprising a waveguide section having its axis positioned directly below said antenna beam axis on said ground plane within the near field of said antenna for intercepting some of that portion of said beam energy that is radiated in the direction of the horizon and reradiating it with a phase shift sufficient for partial cancellation of a portion of said beam energy that is radiated in the direction of the horizon and not intercepted by said phase shifting means, thereby to decrease the antenna power at low elevation angles in the direction of the horizon. - View Dependent Claims (5, 6)
- and 60°
- 7. In a radio communication system utilizing a satellite link and a phased array circularly polarized antenna on the ground, means for improving the ratio of the vertical to the horizontal axis of a circularly polarized antenna beam at elevation angles near the horizon comprising a waveguide section having its axis positioned directly below said antenna beam axis, and within the near field of said antenna, for intercepting a portion of the energy radiated in the direction of the ground and reradiating it with a phase shift for partial cancellation of the portion of energy not intercepted by said phase shifting means, thereby to decrease the antenna power at low elevation angles and improve the axial ratio of said circularly polarized antenna.
Specification