Abstract: For broadcast transmission of Differential GPS data signals, a vertical array antenna provides broad band omnidirective phase-progressive radiation with elliptical polarization. Four-dipole sub-arrays use diagonally aligned two-piece cut and bend dipoles with isolated conductive frontal strip. With these vertically arrayed sub-arrays, lower and upper sub-arrays are excited at 70 percent amplitude and respective plus and minus 90 degree phase rotation relative to middle sub-array, for optimized performance with low elevation lobing. Divided transmission line operation provided by the frontal strip of appropriate length achieves double-tuned dipole performance with very low VSWR over the operating band.

Abstract: A dual-radiator whip antenna to operate over a 30 to 450 MHz frequency band includes a high frequency dipole above a low frequency monopole. The outer conductor (30) of a coaxial line is configured to operate as a monopole. Above the upper terminus of the outer conductor, an extension (32a) of the inner conductor (32) is configured as the upper arm of a dipole. An upper length of the outer conductor also functions as the lower dipole arm. With a single antenna port (13), a diplexer and other feed elements separate signals into high and low frequency bands respectively coupled to the dipole and monopole radiators. Increased high frequency range results from positioning of the center of radiation of the dipole above the monopole.

Abstract: A self-contained four-dipole element provides a 360 degree phase-progressive-omnidirectional (PPO) circularly polarized antenna pattern. Via a single signal port, a PPO excitation network incorporated into the element excites the four dipoles at phases differing by successive 90 degree increments. The four-dipole element is adapted for efficiently reproducible fabrication using printed circuit techniques. Antennas employing a stack of the elements provide a hemispherical antenna pattern with PPO circular polarization and a sharp cutoff below horizontal. For GPS reception in Differential GPS aircraft landing applications, a 21 element antenna provides multipath suppression and a unitary phase center enabling avoidance of signal phase discrepancies. More or fewer elements may be employed in other applications.

Abstract: Low impedance loop antennas utilize a loop separated into a plurality of radiating segments fed in parallel. A four point feed loop antenna, including radiating segments 12, 13, 14, 15 had a measured input impedance varying from 1.8 to 5.8 Ohms over a range of 5 to 15 MHz, without excessive radiation Q degradation. An incorporated feed network includes transmission line segments, with conductors on opposite surfaces of a thin substrate, connecting the radiating segments to a centrally mounted coaxial connector for parallel excitation. Operating bandwidth of the loop antenna is determined by the characteristic impedance of the transmission line feed segments. Low impedance loop antennas which are small relative to operating wavelength can be fabricated on a thin flexible substrate for field transport and use. Incorporation of the antenna into a jacket or other clothing enables field use while minimizing restriction of activity of the user.

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: 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: 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: 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: 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: 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: A relative time offset is measured between transmission of a downlink signal from a cellular radio network base station, and a reference signal (e.g., sync word) included in an uplink signal received at the base station from a network subscriber. If the measured time offset is within a determined range, the uplink signal is judged to originate from a subscriber which is validly assigned to the base station, and the base station will continue to track the valid uplink signal. If the relative time offset is outside the determined range, the uplink signal is judged invalid, e.g., to originate from an interfering co-channel subscriber assigned to a remote base station. The receiving base station will then inhibit tracking of the invalid uplink signal.

Abstract: A non-imaging antenna system for the Instrument Landing System (ILS) utilizes a spatial filter network to provide a glideslope beam at a positive angle, while providing a null effect at a corresponding negative angle to reduce energy reflection at the glideslope angle. Four radiating elements, each including dipoles and a corner reflector, can be used as two overlapping vertical arrays of three elements each. A magic-T input junction is used to provide sum and difference glideslope beam signals to the overlapping arrays. The radiated signals of the two overlapping arrays provide aircraft guidance signals enabling an approaching aircraft to derive indications of high or low departures from the desired glide path. The array apertures may also be tilted from vertical to avoid coning effects of prior ILS antennas. Guidance signals compatible with the current ILS are provided, while avoiding site limitations, snow cover and other operating deficiencies of prior ILS antennas.

Abstract: Antenna systems particularly suited for reception of GPS satellite signals include a vertical stack of element arrays. Each array, which may comprise four dipoles positioned around a central axis, receives signals phased to produce a circularly polarized 360 degree progressive phase radiation pattern around the axis. By rotating in azimuth the radiation patterns of certain of the element arrays and controlling the amplitude of signals applied to different arrays in the stack of arrays, a circularly polarized radiation pattern can be provided encompassing the entire upper hemisphere above the horizon, with a sharp pattern cutoff at or slightly below the horizon. A seven array stack of individual arrays each including four angled dipoles, with a distribution network for providing signals of desired relative phase and relative amplitude to each of the 28 included dipoles, is described.

Abstract: A field monitor in the near field receives an antenna signal which approximates that which would be received by the monitor if located in the far field. In one aspect of the invention, the antenna signal is produced by an array of spaced apart receiving elements. In another aspect of the invention, the signal received from a near field sampling antenna is passed through a signal processor having the necessary characteristics to construct from the sample a signal corresponding to that which would have been received in the far field. Antenna element arrays are also used as plane wave sources permitting antenna testing with a radiating path length of one-eighth or one-quarter of the far field distance. Compact indoor antenna test ranges are also provided.

Abstract: A compact wide-band panel antenna is modified to provide a dual-mode antenna system with improved operation, particularly in the presence of interfering signals and varying reception conditions in mobile communications applications. A hybrid junction arrangement is used to combine received signals in sum and difference modes suitable for adaptive processing. Signal transmission is provided by reciprocal operation, with a circulator incorporated for signal isolation. The dual mode capability provides previously unavailable performance in a small, economical broad-band antenna.

Abstract: A field monitor in the near field receives an antenna signal which approximates that which would be received by the monitor if located in the far field. In one aspect of the invention, the antenna signal is produced by an array of spaced apart receiving elements. In another aspect of the invention, the signal received from a near field sampling antenna is passed through a signal processor having the necessary characteristics to construct from the sample a signal corresponding to that which would have been received in the far field. Antenna element arrays are also used as plane wave sources permitting antenna testing with a radiating path length of one-eighth or one-quarter of the far field distance. Compact indoor antenna test ranges are also provided.

Abstract: A microwave landing system, i.e. MLS, monitor utilizes phase conjugate digital signal processing of near field signals in order to provide an accurate estimate of the signal in the far field. Because of the use of phase conjugate processing, this near field monitor can be located close to the MLS antenna without significant error. This is possible because of the unique relationship of the MLS signal modulation frequencies and the near field geometry.

Abstract: Airborne navigation receivers are designed to derive navigation information with accuracy immune to beam asymmetry errors. Scanned navigation beams of the Microwave Landing System are subject to asymmetry causing beam center measurement errors at power levels other than a standard level 3dB down from peak. Dwell gate and split gate type receivers achieve error immunity through offsetting of errors at power levels above and below a standard power level.