Showing papers on "Antenna array published in 1972"

Planar dipole array mounted on dielectric substrate

Abstract: An improved microwave antenna system employs a flat or planar array of radiating elements and, behind it, a distribution network of feeding circuit portions. The radiating elements and distribution network are physically separated by two wire connections and each feeding circuit portion terminates in a balun aligned with an associated dipole pair. The assembly includes a mounting frame and is of sandwich form incorporating frame portions therein so that the whole is an integral and rigid assembly. The antenna array is provided with a protective cover sheet arrangement and the frame circumscribes and covers the edges of the sandwich assembly.

High-discrimination antenna array for capacitance-responsive circuits

Abstract: A multi-element antenna array for use with capacitanceresponsive circuits to enable discrimination between human occupants and animals or packages resting on an automobile seat.

Dipole antenna array

Abstract: An antenna array is disclosed for generating and directing a narrow beam or beacon of wave energy along a predetermined path. Illustratively, the antenna array includes a plurality of dipole elements disposed upon a substantially flat support member and connected by a distribution circuit through a single transition to an axial input cable. Significantly, the distribution circuit takes the form of an insulating member upon either side of which are disposed electrically conductive elements for establishing across the dielectric member a balanced conduit for the passage of high frequency signals (or waves) to each of the dipole elements. Further, the distribution circuit serves to divide and to appropriately distribute the input signal to each of the dipole elements of the array. A shell housing is disposed about the distribution circuit to provide in combination with the plurality of dipole elements an effective shielding therefore and also to provide a reflective surface to appropriately direct the discrete wave generated by each of the dipole elements.

Antenna array for aircraft navigation system

Abstract: An electronically phased control antenna array having a number of radiators which are to be controlled so as to form two beams respectively pointed toward two separate earth satellites in an aeronautical satellite navigation system and wherein the two antenna arrays are controlled through a Butler matrix comprising a distribution network having phase rotation elements and wherein a plurality of outputs which differ in phase are selectively obtained so as to control the direction of the antenna beam, thus maintaining the antenna arrays respectively pointed at the satellites. The selection of the switching control for the matrices which control the antenna arrays may be accomplished by the use of a computer which has a memory for programming the switching in response to a prior flight path over the same region. Alternatively, the outputs from the antenna arrays and matrix may be sampled and the switches of the matrices controlled so as to obtain the largest signal thus assuring that the arrays are pointing toward the satellites.

Dual frequency array

Abstract: An antenna array having two repetitive radiator systems in a single aperture, operating in two distinct frequency ranges. Each radiator system includes an open-ended, circular waveguide and a parallel plate waveguide. A monopole or a dipole is situated between the plates of the parallel plate waveguide and normal to them. The dimensions of the waveguides and the spacings between them are chosen to provide isolation between the frequency ranges.

On designing a supersynthesis antenna array

Abstract: An analytical approach to the design of a super-synthesis antenna array is applied in this paper. It involves isolation and separate optimization of the influence of different parameters on the sampling of the spatial frequency components. The approach requires a detailed understanding of the geometry of tracking by an ensemble of baselines, but it gives a nearly optimum array design without much help from a computer. A feature of this design is that by simply doubling the array elements, the synthesized main beam area of the array is reduced 16 fold. Extensive computations have been used to demonstrate this extraordinary result.

Phase optimization of antenna array gain with constrained amplitude excitation

Abstract: The formulation of antenna array optimization with variable phase and constant amplitude excitation is presented. The method shown using steepest ascents is general in that a nonlinear performance index expressible as a ratio of Hermitian quadratic forms can be optimized. Directive gain optimization of a linear array of isotropic elements is illustrated and compared with gain optimization using variable excitation. Endfire gain is emphasized and compared to the Hansen-Woodyard condition showing that the Hansen-Woodyard condition is not optimum in the directive gain sense for a discrete endfire array. In addition a 0.4\lambda spaced linear array is optimized using phase only for scanning from endfire to broadside.

Antenna array for grating lobe and sidelobe suppression

Abstract: A circular antenna array comprises module antennas arranged generally in rings in a plane. Although the module antennas are arranged in a systematic pattern on centers which are so far apart that grating lobes would ordinarily occur, the grating lobes are substantially eliminated because of the particular locations selected for the modules. The centers of the modules in each ring are unsymmetrically located with respect to the centers of the modules in the other rings. The level of sidelobes is reduced by providing space density tapering in only the outermost ring of module antennas. In rings other than the outermost ring, the module locations permit achievement of a high aperture illumination efficiency.

Monopulse radar antenna array feed network

Abstract: An array antenna system and feed network providing sum-anddifference monopulse transmission and reception. To permit independence of its sum and difference excitations, the array may be divided into four or more separate subarrays which are arranged in pairs symmetrical with respect to the center of the array and interconnected through sum and difference couplers selected to optimize the sum beam gain and the difference beam angular sensitivity. To further optimize the difference beam pattern, one or more of the array elements on each side of and nearest to the array center are intercoupled through a ''''meaner'''' network which at least partially cancels the antiphased difference excitation for these elements while leaving their equiphased sum excitation unchanged, to thereby lower the difference beam sidelobe level without detriment to the sum beam pattern.

Multiple beam retrodirective array with circular symmetry

Abstract: A method and apparatus for obtaining automatic, selective retrodirective performance from a circularly symmetric antenna array. This system may be employed in an active or passive manner and accomplishes selective retrodirectivity by manipulation of beam terminals of a multiple beam matrix which in turn controls a multimodal network. The combination of the two matrix networks provide N separate beams from the circular antenna array. Also, by providing gain networks, control of the reradiated beam pattern is possible. This system has the ability to identify the angle of incidence of any particular transmission, and is particularly suited for navigational beacon systems since the reradiated signal can provide bearing information in response to interrogation.

High energy microwave defense system

Abstract: A defense system wherein a radar intercepts and follows a target and includes an antenna array and a low level source of microwave energy for exciting the elements of the array to produce radar returns and define the path. A microwave storage reservoir is supplied upon demand with high energy microwave energy and is coupled to microwave feed channels leading to the elements of the antenna array. Microwave dump switches at the juncture of the channels and the reservoir control flow of energy from the reservoir. Control means responsive at least in part to the presence of returns periodically actuate the dump switches for flow of microwave energy from the reservoir to the target via the antenna array.

Shortened turnstile antenna

Abstract: An electrically short turnstile type antenna array which effectively provides vertical or overhead right or left hand circularly polarized coverage in for example satellite communications from a very restricted space volume as characterized particularly in submarine or aircraft antennas. A pair of electrically short dipoles are arranged normal to each other with the axes thereof intersecting at their mid-points. Coaxially arranged about each leg of these dipoles is an open-ended cylindrical sleeve. The feed to the array is by way of a coaxial cable running to the inside of the coaxial cavity formed by one of the sleeves in an end-feed orientation. A mutual coupling link couples signal energy from the inside of the fed coaxial cavity to the inside of one of the coaxial cavities associated with the other dipole. The entire array is mounted on a support mast less than one-eighth lambda from the horizontal base portion of a tin can-shaped ground plane whose vertical sides are sufficiently high to substantially house the array.

Radio frequency antenna system

Abstract: Tactical radio navigation systems provide distance measuring information to an interrogating aircraft in response to pairs of interrogation pulses received at a beacon transponder, the system also provides bearing and identification information. The transponder receives pairs of interrogation pulses which are decoded into a single pulse for operation of a reply transmitter. Bearing, distance and identification determining signals are generated by the reply transmitter and its antennas. A single antenna functions to both receive the interrogation pulses and radiate the position determining signals. To provide the required bearing information, the antenna radiates pulses from a central antenna array that is stationary with respect to a support housing. These pulses are modulated at a 15 Hz frequency by parasitic elements rotating around the stationary central array. Further modulation of the transmitted pulses at a 135 Hz frequency, superimposed on the 15 Hz frequency, is provided by additional parasitic elements also rotating about the central antenna array. Both the low band frequency parasitic elements and the high band frequency parasitic elements have a configuration to provide improved radiation from the antenna above the horizontal. Also to improve the antenna radiation pattern, the 135 Hz parasitic elements are positioned on a rotating drum of a dielectric material, such as fiberglass. To still further improve the amount of radiation energy above the horizontal reference, radio frequency chokes are coupled to the central antenna array in the feed line from the signal transmitter.

Nonuniformly optimally spaced antenna array

Abstract: The object of this invention is to provide a new nonuniformly spaced antenna array, where the most optimum positions of the array elements, and their corresponding amplitudes, are systematically determined by a rigorous synthesis technique of the given radiation pattern, and/or its requirements and specifications, in order to achieve it with the minimum possible number of array elements. This new array will be designated the Nonuniformly, Optimally Spaced Antenna Array, or in short, the NOSA Array.

Amplitude steered array

Abstract: A spin stabilized satellite has an electronically despun antenna array comprising a multiplicity of peripheral antenna elements A high gain energy beam is established by connecting a suitable fraction or array of the elements in phase The beam is steered or caused to scan by switching elements in sequence into one end of the array as elements at the other end of the array are switched out The switching transients normally associated with such steering are avoided by an amplitude control system Instead of abruptly switching from one element to the next, a fixed value of power is gradually transferred from the element at the trailing edge of the array to the element next to the leading edge Thus, as the satellite rotates, power is reduced on one element and power is increased on the other element thereby avoiding switching transients and maintaining constant total array power at all times In terms of the beam, this action smoothly advances the energy and array phase center around the satellite whereas in a conventional switching system the energy and array phase center are caused to jump around the satellite in steps Such phase discontinuities in particular can cause serious degradation to the performance of communication systems passing phase modulated data

Rotating beacon antenna with polarization filter

Abstract: TACAN antennas emit modulated radiation from parasitic reflecting elements associated with a central array having radiating elements coupled to an energizing source. Signal energy from the TACAN antenna is preferably radiated in a plane perpendicular to the surface of the earth. Cross polarization components of the radiated signal are absorbed by resistive wires located in the radiation path from the central antenna array. These resistive wires are mounted around the supporting structure of the TACAN antenna.

Antenna array with pattern compensation during scanning

Abstract: An array is made of elemental radiators with an adjustable aperture controlled by a magnetizing field established within a magnetic section of the radiator. The broadening of the radiation pattern resulting from large amplitude scanning is compensated through aperture control of the individual radiators patterns in the array by means of the magnetizing field within said radiator.

Electronically variable beamwidth antenna

Abstract: Means for obtaining an approximate 2:1 change in beamwidth electronically in an antenna system comprised of a linear array of elements Means are coupled to one of two traveling wave tubes (TWT) which feed the array for selectively serrodyning the signal fed to said one TWT, resulting in a frequency shift of the signal feeding one half of the array with respect to the signal feeding the other half With the serrodyning means deactivated, all of the antenna elements are fed in-phase rf signals and a conventional linear array results providing a narrow beamwidth along the electrical boresight of the array With the serrodyning means activated and since beamwidth is inversely proportional to aperture size, each half of the antenna array is fed by separate respective coherent signals whereupon two independent beams illuminating the same angular sector will be formed having a beamwidth approximately twice that of the whole non-serrodyned array

Wide angle microwave scanning antenna array with distortion correction means

Abstract: A wide angle microwave scanning antenna array includes an assembly of two stationary, parallel, concentric, spaced cylindrical surfaces providing a path for microwaves A rotating waveguide feeds microwave energy into one end of the assembly and a flat focusing lens at the output end of the assembly radiates the microwaves in a scanning plane and focuses the waves at a point moving in the plane A helical mirror in the assembly reflects the microwaves from the input to the lens at the output To correct for distortion and increase the angular range of distortion free scanning, a cylindrical corrector lens is located in the assembly between the input and the mirror

Broad band spiral antenna

Abstract: Antenna elements for substantially circularly-polarized electromagnetic energy are shown. The disclosed elements, formed on a tapered form having an elliptical cross section, are particularly well suited for use as elements in an antenna array because such a cross-sectional shape permits individual elements to be more closely positioned with respect to each other, thereby raising the frequency of the electromagnetic energy at which grating lobes occur.

Linear or planar retrodirective antenna system

Abstract: A method and apparatus for obtaining automatic retrodirective performance from a linear or planar electromagnetic antenna array. The system may be employed in an active or passive manner and accomplishes selective retrodirectivity by the manipulation of the beam terminals on a multiple beam matrix. Also, control of the reradiated beam pattern is possible. Furthermore, this retrodirective system can also identify the angle of incidence of any particular transmission, and may therefore be employed as direction finding equipment.

Low loss modulation system for use with antenna array

Abstract: An antenna array has paired radiating elements which are modulated in phase opposition. Such modulation is accomplished by means of semiconductor modulator elements, one of such elements being connected to the feed line for each of the paired antenna elements. Modulation signals are fed to the paired semiconductor elements in phase opposition relationship to vary the effective impedance of such elements accordingly, thereby causing the power fed to one of the associated paired antenna elements to increase while that to the associated paired element is decreasing, this in accordance with the modulation signal, the sum of the power radiated by the paired elements remaining constant. Power losses are thereby minimized.

Variable squint and beamwidth amplitude monopulse radar

Abstract: In an amplitude monopulse radar, a cross coupling network between the respective feeds of a dual-radiator, angle measuring antenna array, couples energy from each feed into the other, with variable phase and amplitude adjustments to the energy coupled from one feed to the other feed, thereby providing, in effect, an artificial alteration in the intercoupling between the elements of the antenna array, in a manner to control the squint angle (or angle off of boresight) and beamwidth of the array.

Microstrip technology and its application to phased array compensation

Abstract: A systematic analysis of mutual coupling compensation using microstrip techniques is presented. A method for behind-the-array coupling of a phased antenna array is investigated as to its feasibility. The matching scheme is tried on a rectangular array of one half lambda 2 dipoles, but it is not limited to this array element or geometry. In the example cited the values of discrete components necessary were so small an L-C network is needed for realization. Such L-C tanks might limit an otherwise broadband array match, however, this is not significant for this dipole array. Other areas investigated were balun feeding and power limits of spiral antenna elements.

On Designing a Supersynthesis Antenna Arrav J

Abstract: An analytical approach to the design of a super- synthesis antenna array is applied in this paper. It involves isolation and separate optimization of the influence of different parameters on the sampling of the spatial frequency components. The approach requires a detailed understanding of the geometry of tracking by an ensemble of baselines, but it gives a nearly optimum array design without much help from a computer. A feature of this design is that by simply doubling the array elements, the synthesized main beam area of the array is reduced 16 fold. Extensive computa- tions have been used to demonstrate this extraordinary result.

Radiation from a Continuous Semi-circular Arc Antenna Array

Abstract: The nature of radiation from a continuous semi-circular arc antenna array has been theoretically studied. The pattern expressions are made to appear in closed mathematical forms by making use of an analysis analogous to one presented elsewhere by the authors in connection with spiral antenna arrays. The vertical radiation patterns have been numerically computed and graphically discussed.

A New Log-periodic Structure with Asymmetric Dipole Elements

Abstract: In this communication an approximate analysis of a new log-periodic structure made of asymmetric dipole elements is presented. A simple mathematical expression for the radiation pattern has been derived using the concept of conventional linear antenna array theory. Theoretical calculations have been made and the plots of E- and H-plane patterns have been given for various values of ψ, the separation angle between the two halves of the LPD antenna. An effort has also been made to show the variation of the radiation pattern for various values of asymmetry ratio AR.