Abstract: An amplitude monopulse direction finding system is disclosed. The system is built around a circular array with a circular lens in which the antenna elements and array ports are larger than in conventional systems. The oversized antenna elements and array ports provide a wide range of operating frequencies for the direction finding system. Additionally, the direction finding system contains an omni-directional probe at the center of the lens to detect the presence of signals. In an alternative embodiment, each array port is split into two halves which can be combined in different ways to produce different beam patterns, allowing the beam pattern providing the best signal to noise ratio to be selected. Also, built-in-test circuitry is described.

Abstract: An array antenna system producing beams with widths constant with scan angle. The antenna array is fed by a microwave lens. The beam ports of the lens are disposed along an arc displaced from the focal arc of the lens. The distance between the arc and the focal arm decreases from a maximum amount at the center of the lens to a minimum amount where the arc intersects the focal arc.

Abstract: An array antenna is shown, the disclosed antenna having an effective cross-sectional area which is lower than its physical cross-sectional area. The reduction in effective cross-sectional area is effected by: (a) fabricating the reflector for the array antenna from spaced wires; and, (b) curving the entire array and its reflector.

Abstract: A radio frequency antenna system comprising a plurality of antenna elements arranged in an array, such array comprising a pair of subarrays of antenna elements coupled to a pair of electromagnetic lenses. Each lens includes a plurality of array ports, the plurality of array ports of the first lens being coupled to the antenna elements of a first one of the pair of subarrays, and the plurality of array ports of the second lens being coupled to the antenna elements of a second one of the pair of subarrays. The first lens further comprises a first set of beam ports, and the second lens further comprises a second set of beam ports, the first and second sets of beam ports being arranged to form corresponding first and second sets of interleaved beams of radio frequency energy.

Abstract: A reflector type radio frequency antenna having: a feed for producing a difference radiation pattern with a cone-shaped null region; and, a reflector having a surface disposed to reflect a portion of the energy in the difference radiation pattern and having the edge disposed in the cone-shaped null region. With such arrangement, since the edge of the reflector is disposed in the null region of the difference radiation pattern such edge is not radiated with energy which could otherwise illuminate such edge, scatter, and thereby generate unwanted side lobes in the free space antenna pattern.

Abstract: A radio frequency antenna having a parabolic reflecting surface and an array of feeds disposed adjacent the focal point of the parabolic reflecting surface, such feeds providing a predetermined amplitude and phase distribution to radio frequency signals passing to such feeds, each one of such feeds passing such energy in the same propagation mode. The energy passing through each one of the feeds is reflected from the reflecting surface and combines at the radiating aperture to provide, in free space, an antenna pattern having relatively low sidelobes over a relatively wide band of frequencies. The array of feeds includes a waveguide section having opposing outer wall portions and a plurality of conductive members disposed between the opposing outer wall portions to provide, with the outer wall portions, a plurality of channels.

Abstract: A radio frequency beam forming network is disclosed wherein a plurality of antenna feed elements arranged in the focal plane of a radio frequency lens is coupled to corresponding input ports of a radio frequency energy distributing means. Output ports of such radio frequency energy distributing means are coupled to a receiver/transmitter through different paths. Disposed in the different paths are active elements, including variable phase shifters and attenuators. The active elements, in response to control signals, provide proper attenuation and phase shift to the signals passing therethrough thereby to form a desired antenna beam. Such antenna beam is comprised of one or more "spot" beams. With such arrangements failure of a single one of the active elements will only slightly degrade system performance without resulting in a complete loss of any one of the "spot" beams.

Abstract: An antenna element is disclosed having a printed circuit parallel plate region with a parabolically shaped reflecting wall and a flared radiating section. The flared radiating section is disposed along an aperture which intersects the axis of the parabola at an acute angle. A microstrip feed formed integrally with the printed circuit parallel plate region is offset from the reflecting wall and is adapted to introduce radio frequency energy at the focal point of such reflecting wall. Load material is disposed adjacent to the focal point to absorb radio frequency energy reflected by the aperture thereby improving the VSWR of the feed. Such arrangement enables close element-to-element spacing in an array, thereby substantially eliminating grating lobes while enabling intermeshing of the elements to provide port and starboard array antennas.

Abstract: A radio frequency multibeam array antenna is disclosed wherein a beam forming network includes a first set of vertically disposed parallel plate lenses coupled between a matrix of radiating elements and a second set of horizontally disposed parallel plate lenses. With such a beam forming network a plurality of narrow pencil-shaped beams of radiation may be formed over a relatively large solid angle.