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: Prior methods of reading MaxiCode dataforms have been subject to reduced resolution image scaling and processing and speed constraints of Fourier transform computations. Described spatial domain data extraction methods provide bull's eye center location by T-sequence pixel pattern analysis, axis identification by moment analysis of data cell pairs, and integral width square wave analysis of illumination transitions to avoid reading-line cell fragmentation. The center and top of a MaxiCode are identified in high-resolution pixel data, without scaling reduction or Fourier type frequency domain processing. Data is extracted serially from rows of data cells by sampling along lines of pixels aligned by fragmentation analysis so as to traverse complete rows of data cells. Dynamic thresholding accurately defines illumination value transitions between adjacent linear groups of data cells, each group consisting of one or more data cells of the same reflectivity.

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: 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: Probabilities of usage of specific words are evaluated based on frequency of usage in the selected language, such as English. Syntax type probabilities of word sequencing are evaluated through (i) rules based on transitional probability of use of two particular words in sequence in English usage and (ii) rules based on probability of relative positioning of words of particular word categories (e.g., nouns and adjectives) in a sentence structure in English usage. A word trellis or lattice represents choice paths for alternative sentence structures. By selecting the path with the highest probability values, highly accurate sentence reconstruction is provided.

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).

Abstract: Vehicle arresting blocks of cellular concrete are usable to safely slow travel of an object and may be used to construct an aircraft arresting bed at the end of an airport runway. For such purposes, cellular concrete blocks must be fabricated to exhibit compressive gradient strengths of predetermined values to provide sufficient, but not excessive, deceleration forces on an object. Material uniformity characteristics must be met to avoid unacceptable drag force variations, so that arresting blocks desirably exhibit a predetermined compressive gradient strength (e.g., a 60/80 CGS) over a depth of penetration of 10 to 66 percent of block thickness. A 60/80 CGS will typically represent an average compressive strength of 70 pounds per square inch over such depth of penetration. Prior applications of cellular concrete typically involved meeting minimum strength values and the production methods did not meet uniformity or compressive gradient strength predictability as required for arresting blocks.

Abstract: Vehicle arresting beds, for installation at the ends of aircraft runways, are effective to safely decelerate aircraft entering the bed. The arresting bed is assembled of a large number of blocks of cellular concrete having predetermined compressive gradient strength, so that aircraft landing gear is subjected to drag forces effective to slow a variety of types of aircraft, while providing deceleration within a safe range of values. An arresting bed typically includes an entry region of a depth increasing from 9 to 24 inches formed of blocks having a first compressive gradient strength. A second region, which may be tapered into the first region and increase in depth to 30 inches, is formed of blocks having a greater compressive gradient strength. An aircraft thus experiences increasing drag forces while it travels through the bed, to provide an arresting capability suitable for a variety of aircraft.

Abstract: A 90 degree azimuth beamwidth is achieved in a narrow cellular antenna, by inclusion of sidewalls. To improve front-to-back performance, slot radiating elements extending through the sidewalls re-radiate signals behind the antenna. Signals re-radiated from the slot elements are effective to partially cancel signals otherwise radiated behind the antenna as a result of diffraction. H-shaped slots are described for sidewall use and side-to-side slots are described for endwall use. Slots may be dielectrically loaded by contiguous portions of a radome.

Abstract: Performance of multibeam cellular antenna systems is improved by use of space diversity in antenna placement and angle diversity in antenna alignment. Space/angle diversity is achieved on a single tower structure (20) by placement of eight antennas (B1-B8) in pairs at four spaced locations (I, II, III, IV) at the tower corners. Antennas are placed with an orthogonally directed pair at each location. For each orthogonal pair (e.g., B1 and B2 at location I) there is an antenna located at a different corner which is pointed between the orthogonal directions (e.g., B5 at location II). Antenna placement and alignment for achieving space/angle diversity in triangular tower configurations are also described.

Abstract: Multi-beam antenna feed networks employ more aperture ports (e.g., ports I, II, III, IV and V) than beam ports (e.g., ports A, B, C and D) to achieve low sidelobe lossless operation, particularly for cellular communications. With five aperture ports, signal value outputs at the aperture ports represent orthogonal outputs having phase gradients effective to provide a four beam radiation pattern. The feed arrangement includes directional couplers (e.g., C11, C21) and phase shifters (e.g., P22, P23) intercoupled between the beam ports and aperture ports to provide the desired orthogonal aperture excitation. An example of specific directional coupler and phase shifter circuit values for a matrix network for a four beam port to five aperture port feed network configuration is provided.

Abstract: An image sensor array system is addressable to enable readout of randomly selected image data from any one or more individual sensor cells, for any selected image area (13), or for the entire image area (15). The sensor array (16) is accessed by horizontal and vertical readout circuits (22 and 24) under the control of address signals from an address unit (20). Location signals, from a source (12), indicative of a selected image area (13) may be used by the address unit (20) to provide address signals representative of the location of a specific sensor cell or area (13) of the array including image data of interest. Under the control of the address signals, image data from cells at the intersection of array lines and columns are sampled by sampling devices (26-32) and provided as output signals representative of the selected portion of the image area at an output port (34). Simplified readout can be provided for oblique line components of images.

Abstract: Single stroke text entry via a telephone keypad is subject to ambiguities resulting from the overloading of three letters on one key. After text is entered the three letter per position code block represented by the key strokes for a word position is hashed to all matches in a stored dictionary type word list. The resulting word group of alternative word choices for that word position is subjected to probability analysis. Probabilities of usage of specific words are evaluated based on frequency of usage in the selected language, such as English. Syntax type probabilities of word sequencing are evaluated through (i) rules based on transitional probability of use of two particular words in sequence in English usage and (ii) rules based on probability of relative positioning of words of particular word categories (e.g., nouns and adjectives) in a sentence structure in English usage. A word trellis or lattice represents choice paths for alternative sentence structures.

Abstract: Prior methods of reading MaxiCode dataforms have been subject to reduced resolution image scaling and processing and speed constraints of Fourier transform computations. Described spatial domain data extraction methods provide bull's eye center location by T-sequence pixel pattern analysis, axis identification by moment analysis of data cell pairs, and integral width square wave analysis of illumination transitions to avoid reading-line cell fragmentation. The center and top of a MaxiCode are identified in high-resolution pixel data, without scaling reduction or Fourier type frequency domain processing. Data is extracted serially from rows of data cells by sampling along lines of pixels aligned by fragmentation analysis so as to traverse complete rows of data cells. Dynamic thresholding accurately defines illumination value transitions between adjacent linear groups of data cells, each group consisting of one or more data cells of the same reflectivity.

Abstract: A set of complementary block units suitable for wall construction includes a first block unit of cylindrical contour (e.g., circular, elliptical, hexagonal) and a plurality of interstitial block units for interfacing and supporting the circular or elliptical block units when arranged in a suitable pattern. Each block unit may include a peripheral groove or ridge suitable for receiving grouting. The blocks are formed with surfaces having complementary shaped edges, such that any one of a plurality of interstitial block units will interface with any cylindrical block unit of a set. Three configurations of interstitial units enable combination with cylindrical units in edge, corner and internal positions within a wall or window structure.