Abstract: Omnidirectional cellular coverage may be provided by installing four 90 degree antennas on the sides of a tower. However, in a prior system pattern uniformity will be destroyed by nulling effects if the tower width causes the lateral separation between adjacent antennas to be large. Nulling effects in areas of overlap between beams of adjacent antennas are avoided by providing an omnidirectional pattern characterized by signal polarization which changes with azimuth. Cross polarization of adjacent antennas is achieved by providing North and South antennas with +45 degrees linear polarization and East and West antennas with -45 degrees linear polarization (alternating antennas with right and left circular polarizations may also be used). Portable cellular receivers for use with the antenna system may typically utilize antennas with either vertical or horizontal linear polarization.

Abstract: Double-tuned radiating elements 10 for cellular antennas are configured to enable stamping in one piece from flat sheet metal. Unitary construction incorporates a radiating section 22, an exciter section 14 and a balun section 12 in each radiating element. After the element is formed in one flat piece, a 90 degree bend is made along bend line BL to position radiating section 22 normal to the exciter and balun sections. When mounted in an antenna with the exciter and balun sections 14 and 12 parallel to a conductive ground plane surface, radiating section 22 extends forward normal to the ground plane surface. Radiating section 22 and exciter section 14 are fed by direct coupling to balun section 12, via shared current paths.

Abstract: A two-axis satellite antenna mounting and tracking assembly including a universal joint for mounting the antenna to support structure. A pair of linear actuators offset at 90.degree. to each other about the universal joint are operated in full-on/full-off fashion to control the azimuth and elevation orientations of the antenna. Satellite tracking is effected by maximizing received signal strength.

Abstract: Cellular antenna systems are provided for airship-type support at a position in the stratosphere. A single antenna system (20) may provide cellular communication for earth-based users located anywhere within a circle 400 miles in diameter (10). By use of array assemblies (21a) each providing 12 side-by-side beam positions per quadrant, with higher and lower elevation beams (32a', 36a') at each beam position, coverage can be provided for 96 cells arranged side-by-side in inner and outer annular bands (10). A turnstile-type antenna (26) provides coverage for a 97th central circular cell. By allocation of available groups of cellular frequencies in repetitive patterns around the outer annular band (1-6, FIG. 1), with frequency reuse in offset positions around the inner annular band, 16 times frequency reuse is provided while maintaining acceptable co-channel interference levels.

Abstract: One aspect of the invention relates to a reflective mat useful to provide an electromagnetically reflective surface on a high-frequency radio antenna. In one version of the invention, the reflective mat includes a conductive mat shaped to conform to a signal receiving surface of an antenna core. The conductive mat has a core contacting surface, which is coated with an adhesive material for joining the conductive mat to the receiving surface, and a signal reflecting surface which is coated with a curable finishing material.

Abstract: Without use of separate auxiliary antennas, adaptive nulling automatically reduces jamming or other interference affecting a radar or IFF system. A primary beam forming network utilizes four-port directional coupler devices, each having an ancillary port which would have been resistively terminated in the absence of the invention. Signals from ancillary ports are coupled to an auxiliary beam forming network to form auxiliary beam patterns which are orthogonal to and track steered main beam patterns. Auxiliary signals are received via the auxiliary beam patterns. Least mean square (LMS) control loops operate on a feedback basis to derive weighted auxiliary signals responsive to jamming signals. The weighted auxiliary signals are combined with the primary received signals (which may be sum and difference signals) in reverse polarity, so as to be additively destructive of the jamming signals. Multiple LMS control loops enable nulling of jamming signals simultaneously in sum and difference channels.

Abstract: A dipole array antenna is configured for improved cellular operation by avoidance of metallic contacts which can lead to generation of intermodulation products (IMP). Isolated rectangular dipole radiators 12-17 are electromagnetically excited by perpendicularly aligned non-contacting exciter resonators 40-45. The rectangular exciter resonators 40-45 are integrally formed with microstrip signal distribution feed 18 supported above a ground plane 22. A non-contact RF grounded termination for the outer conductor of coaxial input line 52 uses a quarter-wave microstrip line section 56 to provide a low impedance RF path to ground to avoid IMP. An RF-isolated DC grounding circuit for surge protection includes a parallel combination of quarter-wave line sections 62 and 66. Line section 66 provides an RF open circuit path to a DC grounding post 67. Line section 62 provides a parallel non-contact low impedance RF path to ground, avoiding IMP from flow of an RF current through pressure contact points at post 67.

Abstract: U-dipole radiating elements (10) and associated feed conductors (20, 22) are cut or stamped from brass sheet stock. Each U-dipole (10) is then bent up at 90 degrees to the signal distribution conductor (22) which is supported in front of a reflector (12). The U-dipole element (10) includes a first dipole-type conductor segment (14) connected near one end to a feed segment (20) which is the sole signal feed path to the U-dipole element. A second dipole-type conductor segment (16), which is spaced from and parallel to and coextensive with first segment (14), is connected to the other end of the first segment (14). An antenna may include one or more individual U-dipole elements cut from sheet stock and connected to feed points. In a linear array antenna configuration, a group of U-dipole elements (10a-10b) and associated signal feed network components may be cut in a unitary form from a sheet of conductive material and supported in front of a reflector surface.

Abstract: A low cost array antenna (10) employs U-dipole elements (30) inserted into slots in a printed circuit board (18). Board (18), supported in spaced relation directly by back reflector (12), bears a feed network (22) connected to an input/output port (24). The dipole element (30) is a dual-dipole single-feed element, including parallel coextensive dipole segments (32, 34) attached at one end, with a sole signal feed path via feed segment (36). Feed segment (36) is inserted into board (18) and soldered to a feed point of feed network (22). One or more mounting tabs (38) are also inserted into slots in board (18) and may be fixed in place by soldering to an isolated conductor portion provided on board (18) for this purpose. A dual array antenna (50) includes dipoles (51-54) for left slant polarization reception and dipoles (61-64) for right slant polarization reception.

Abstract: In a cellular type communication system a sector antenna 12 provides coverage of a sector with a relatively low receive gain. A multi-beam antenna 20 covers the same sector with a plurality of narrower beams 21', 22', 23' and 24' providing higher gain. A multi-beam antenna system 10 provides higher gain operation by selecting the one of the narrower beams 21', 22', 23' or 24' currently providing best reception of a signal transmitted by a user and coupling that selected beam to a system receiver 18. Beam selection is accomplished by sequentially coupling each narrow beam to a microprocessor based control unit 40 and storing samples of user signals as received in each narrow beam on a continuing repetitive basis. The stored samples are then analyzed in order to select the beam currently providing best reception.

Abstract: Aircraft-mounted Identification Friend or Foe (IFF) antennas employ a linear array of radiator elements positioned transverse to the boresight axis. With an azimuth determination capability, but lacking elevation resolution, such antennas are subject to coning errors in determining the azimuth bearing of a target at an altitude differential. With use of a linear array (10) of multi-radiator elements (11, 12, 13), an output signal (23) having the characteristic of an amplitude which increases for off-boresight targets is provided. That signal is compared to a typical form of antenna system output signal (22), which has an amplitude which decreases for off-boresight targets. By such amplitude comparison, the angle (.beta.) to a target is determined and used to provide an azimuth correction factor (53). An apparent azimuth bearing (54) subject to coning error can then be corrected (55) to provide the true azimuth angle to a target (56).