Omni-steerable cardioid antenna

Claim 2

An antenna system comprising: coaxial-line cavity radiator means, the cavity being tuned to resonate in two mOdes; radiator circuit means connected to the radiator means for providing said radiator means with excitation signals; RF control means connected to the radiator circuit means and providing a plurality of signals, said RF control means comprising mode selection means for determining either an onmidirectional pattern or an electronically steerable unidirectional pattern, and phaseshifting means for determining the direction of the steerable unidirectional signal, said RF control means having an input port.

Claim 3

The antenna system according to claim 1 wherein: said radiator means is tuned to the TEM mode and the two crossed TE11 modes; said TEM mode is used alone for omnidirection patterns; and a combination of TEM mode and crossed TE11 modes are used for the steerable unidirectional pattern.

Claim 4

The antenna system according to claim 1 wherein said radiator circuit means comprises two input ports, three hybrid junction means and a directional coupler means all of which are interconnected to receive the plurality of signals from the RF control means and provide the excitation to said radiator.

Claim 5

The antenna system according to claim 3, wherein: said hybrid junction means produce equiphase signals for the omnidirection mode; and said hybrid junction means and said directional coupler means provide the signals for the steerable unidirectional mode.

Claim 6

The antenna system according to claim 1 wherein: said mode selection means comprises two transfer switches and a directional coupler; said phase shifting means comprises a 0 - 180* continuously variable phase shifter connected by a switching means to a 0* or 180* step phase shifter.

Claim 7

The antenna system according to claim 5 wherein: said RF control circuit has two output ports; and said mode selection means and phase shifting means are inter-connected to produce a. one of the radiator''s modes on one of the output ports for the omnidirectional pattern and b. simultaneously, both of the radiator''s modes on each of the output ports separately for the steerable unidirectional pattern.

Claim 8

The antenna system according to claim 6 wherein: said radiator means is tuned to the TEM mode and the two crossed TE11 modes; said TEM modes is used alone for omnidirection patterns; and a combination of TEM mode and crossed TE11 modes are used for the steerable unidirectional patterns.

Claim 9

The antenna system according to claim 1 wherein: said radiator means is a coaxial-line cavity radiator comprising four symmetrically located dipoles.

Claim 10

Dual-mode antenna means for radiating an omnidirectional or steerable-cardiord pattern, as desired, comprising: radiating means containing a cavity therein and including at least four coaxial-line dipole antenna means located symmetrically around said cavity, said cavity being excited to radiate electromagnetic energy when said dipole means are energized; and means for feeding signals of two types to said dipole antenna means, the first of which types excites said cavity to radiate an omnidirectional radiation pattern and the second of which types excites said cavity to radiate a steerable cardiord pattern.

Claim 11

Dual-mode antenna means for radiating an omnidirectional or steerable-cardiord pattern, as desired, comprising: radiating means containing a cavity therein and including at least four coaxial-line dipole antenna means located symmetrically around said cavity, said cavity being excited to radiate electromagnetic energy when said dipole means are energized; and means for feeding signals of two types to said dipole antenna means, the first of which types excites said cavity to radiate an omnidirectional radiation pattern and the second of which types excites said cavity to radiate a steerable cardiord pattern.

Claim 12

An antenna as in claim 9, wherein the first type of signal fed to said dipoles excites resonance of said cavity in a TEM mode and the second type of signal fed to said dipoles excites resonance of said cavity in a TEM mode and in a pair of orthogonally related TE11 modes.

Claim 13

An antenna as in claim 9, wherein the diameter of the aperture is approximately 0.9 of a wavelength at the center design frequency and the depth of the coaxial-line cavity is approximately 0.2 of a wavelength at the center design frequency.

Claim 14

An antenna as in claim 11, wherein said feeding means includes rf control circuit means and radiator circuit means, said radiator cIrcuit means including three hybrid junctions, each with a sum ( Sigma ) and a difference ( Delta ) input port and each with two output ports, and a 3 db coupler having an input port and at least two output ports, said TEM signal being fed to the Sigma port of the first hybrid junction, the output ports of which feed the Sigma ports of the other two hybrid junctions, said TE11 signals being fed to the input port of said coupler, one of whose output ports feeds the Delta port of the second hybrid junction and the other of whose output ports feeds the Delta port of the third hybrid junction, the four output ports of said second and third hybrid junctions each being connected to a different one of said dipole elements.