Showing papers on "Antenna array published in 1978"

Large element antenna array with grouped overlapped apertures

Abstract: An antenna for transmitting or receiving, for limited fine scan or wide angle scan, or for producing multiple beams has a plurality antenna radiators or receivers (apertures) in a linear array, coupled to a smaller plurality of antenna networks so that many of the antenna apertures are coupled to two of the networks and the networks are all coupled to a common transmission line. For a spatial scanning system, each network is coupled to the common transmission line through a variable phase shifter so that the radiation patterns of the apertures combine to define a beacon of predetermined fine pointing direction that can be used to spatially sweep a sector by varying the phase shifters according to a predetermined schedule. Furthermore, by shifting the point of feed to the networks, the pointing direction is caused to switch in relatively large steps, from one sector to another sector.

Simultaneous multiple beam antenna array matrix and method thereof

Abstract: Apparatus and method for adjusting the position of radiated beams from a Butler matrix and combining portions of adjacent beams to provide resultant beams having an amplitude taper resulting in a predetermined amplitude of side lobes with a maximization of efficiency

Antenna beam steering controller

Abstract: An electronically scanned phased array antenna system comprises a phase shift controller corresponding to each antenna array element for individually computing a phase shift value which governs the phase of the signal associated with the corresponding antenna element. The computed phase shift values of all the phase shift controllers effect a phased array on the signals of the antenna elements to point the antenna beam in a desired direction. Each of the phase shift controllers is programmed with a predetermined phase shift value increment for computing a sequence of phase shift values at specified intervals of a predetermined time pattern, each new phase shift value being preferably concurrently computed by the phase shift controllers at the specified time intervals. The phased arrays resulting from each of the newly-computed phase shift values of the sequence render the antenna beam to be scanned in a corresponding sequence of desired directions according to the specified intervals, which may be non-uniformly spaced, in the predetermined time patterns. Each predetermined phase shift value increment correspondly programmed into each phase shift controller may be based on a function of the geometric position of the correspondingly associated antenna element in the antenna array.

Automatic direction finding system

Abstract: An automatic direction finding (ADF) system including a direction finding antenna array which connects to a radio receiver to process an audio output signal selectively illuminating a segment of a segmented circular visual directional display indicating the direction from which the received signal arrived. In an FM version, the ADF system electronically switches between antennas in the direction finding antenna array alternately incorporating vector information onto the received carrier in a manner that can be phase detected to produce an audio frequency signal within the normal pre-audio bandpass of the receiver. The audio frequency is then demultiplexed to produce separate vector signals. These separate vector signals are then processed for selectively illuminating a segment of the segmented circular visual directional display. When a sufficiently strong signal is not being received, the ADF system sequentially illuminates each segment of the segmented circular visual directional display in a clockwise direction at a rate which can be readily and visably perceived by an operator. This operation conveys the image of circuit activity, is exciting for an operator to watch, and may have the effect of simulating a radar sweep, although it is in no way related to the searching by the receiver. An additional segment is positioned in the center of the display to indicate the processing of a received radio frequency signal by the ADF system.

A reactively loaded aperture antenna array

Abstract: The use of variable reactive loads to control the beam direction of an antenna array consisting of N closely spaced waveguide-backed dielectric-filled rectangular slots is considered. Only the center waveguide is driven (no complex feed network is required for the array), and the other waveguides are short circuited at specified distances to provide reactive loading. The solution uses the method of moments applied to the integral equation for the equivalent magnetic current in the aperture region. The initial, design of the array is obtained by resonating the complex excitation voltages required for maximum gain with all of the elements driven. This is then improved by an optimum seeking univariate search method. Computed results are given for seven- and fifteen-element aperture arrays.

Digital beam former

Abstract: A method and apparatus for forming a set of simultaneous multiple antenna beams. The digital technique utilizes a Fermat Number Transform (FNT) processor which takes the transform of number sequences consisting of the output signals from the elements of a preferably circular, equiangularly spaced antenna array, then forms the complex linear vector product of the transformed signals and a stored beam-forming function, and finally processes the complex linear vector product through an inverse FNT network to generate a set of simultaneous multiple antenna beams. The advantages of utilizing the FNT include reduced hardware requirements, greater processing speed due to a reduction in multiplications required to be performed, and sharper output beams due to the absence in the FNT of round-off errors.

Microwave power transmission beam safety system

Abstract: A system in which the characteristics of a microwave power transmission beam are controlled in accordance with power distribution profiles altered due to the detected presence or entrance of an object into the beam which causes changes that are perceived in various received, reflected and scattered power distribution profiles resulting over various receiving elements of the system An analysis of these changes is made, the results of which are used to reshape, dim or douse the power beam in accordance with predetermined criteria Additionally, a "FAIL SAFE" condition is obtained by employing a beam penetration tester, whose function is to repeatedly test the correct performance of the beam intrusion detecting scheme by presenting a minimal threshold scattering or absorbing cross section while crossing the power beam If the beam penetration tester is undetected by the beam safety system, then the beam control is preconditioned to turn off the power beam Conversely, if the beam penetration tester is successfully detected, then the power beam is allowed to remain on The system comprises a microwave power beam radiator array, a microwave power beam receiving antenna array, the radiator array in one embodiment being located on an orbiting spacecraft and the receiving array being located at a ground station Another embodiment provides a ground based transmitting array and a receiving array aboard an aircraft or airship

Antenna system with multiple frequency inputs

Abstract: An improved antenna system is disclosed in which a single antenna array is simultaneously used in conjunction with several independent radio devices. Isolated and independent radio transmitters are coupled, without any signal cancellation, to each and every one of a plurality of isolated independent antenna elements by a combining network which maintains the isolation between each of the radio transmitters and each of the antenna elements. The combining network comprises an array of hybrid networks and creates a predetermined electrical phase difference between each signal received by an individual antenna element. The antenna elements form a single antenna array consisting of circularly disposed corner reflector antennas. Each reflector independently creates an individual radiation pattern and these patterns combine to form a single desired composite radiation pattern. By maintaining isolation between each of a number of radio transmitters, a plurality of these transmitters may be used simultaneously in conjunction with a single antenna array.

Techniques for cophasing elements of a phased antenna array

Abstract: The present invention relates to a method of cophasing the feed elements of a transmitting or a receiving phased array antenna. To cophase a transmitting antenna, the method entails transmitting a lower sideband and an upper sideband signal from a first and a second one of the feed elements, respectively, while transmitting a carrier signal used to generate the sideband signals on all other feed elements of the array. At each receiver the reference phase angle between the received sideband signals is measured and stored. The above step is sequentially repeated for the first and a third, the first and a fourth, etc., one of the feed elements, and the phase angle measured, subtracted from the reference phase angle, and stored. With the above method, the phase angle between each feed element and the second one of the feed elements is determined and stored and subsequently transmitted back to the transmitter for use in transmitting signals to each receiver. To cophase a receiving antenna, a received signal is modulated at sequential pairs of the feed elements to produce the upper and lower side-band signals and enable the above cophasing sequence to be performed.

Antenna apparatus for bearing angle determination

Abstract: Antenna apparatus for representing a bearing angle includes an antenna array of N antenna elements equispaced around the arc of a circle of at least 90°, and preferably greater than 180° in a plane for receiving microwave energy, microwave power dividing and phase transforming matrix having N input ports respectively connected to the antenna elements and a set of output ports connected to a utilization device for indicating the bearing angle of the incoming microwave energy, and a utilization device including means for measuring the phase difference between signals at pairs of the output ports for representing the bearing angle.

Bi-directional antenna array

Abstract: A bi-directional antenna array is disclosed having at least two vertical loop antennas arranged mutually perpendicular individually operable to produce bi-directional scanning patterns shifted ninety degrees to achieve significant side rejection so that a user can better utilize the congested frequency spectrum.

Digital bearing indicator

Abstract: Apparatus for digitally indicating the bearing angle of a source of microwave energy includes an antenna array of a plurality of antenna elements equispaced about an arc of a circle in a plane. Connected to each of the antenna elements is a different input port of a microwave power dividing and phase transforming hybrid matrix. Some of the output ports of the matrix are connected to input ports of a plurality of digital phase discriminators whose outputs emit a coded combination of binary level signals. The outputs of the phase discriminators are connected to an ambiguity resolving means which transforms the binary level signals to an unambiguous digital word representing the bearing angle.

Parameters of a spherical random antenna array

Abstract: The shape of the beam of a spherical random antenna array is discussed and the main parameters, such as bandwidth, beamwidth and hyperfocal distance are determined.

Parabolic and log periodic antennas combined for compact high-gain broadband antenna system

Abstract: The disclosed antenna system includes a non-conductive parabolic dish, a first antenna array rigidly positioned in front of the dish, and a second antenna array extending through the dish and having radiating elements on either side thereof. In one embodiment, a plurality of conductive strips are disposed on the dish in a polarization selective pattern; the first antenna array generates linearly polarized electric fields that are reflected by the strips; and the second antenna array generates linearly polarized electric fields that pass through the strips. In another embodiment of the invention a plurality of conductive areas are disposed on the dish in a checkerboard frequency selective pattern; the first antenna array generates electric fields in a frequency band that are reflected by the pattern; and the second antenna array generates electric fields in a frequency band that are passed by the pattern.

Frequency translating phase conjugation circuit for active retrodirective antenna array

Abstract: An active retrodirective antenna array having central phasing from a reference antenna element through a "tree" structured network of transmission lines utilizes a plurality of phase conjugate circuits (PCCs) at each node and a phase reference regeneration circuit (PRR) at each node except the initial node. Each node virtually coincides with an element of the array. A PCC generates the exact conjugate phase φ* 1 of an incident signal φ 1 in accordance with the relation R (2φ 0 -φ 1 ) where R is equal to the reciprocal of 1-2/n, and n≧4, using a phase locked loop which combines the phases φ 1 and φ* 1 in an up-converter, divides the sum by 2 and mixes the result with the phase φ 0 in a down-converter for phase detection by the phase φ* 1 from the loop oscillator divided by n. The PRR extracts the phase φ 0 from the conjugate phase φ* 1 by mixing φ* 1 divided by 2 and divided by n in a down-converter and then mixing the phase φ 1 divided by 4 with the result of the down-converter in two cascaded up-converters. Both the PCC and the PRR are not only exact but also free from mixer degeneracy.

Differential backlobe antenna array

Abstract: This specification discloses an antenna system with a left antenna array having a pair of radiators and a right antenna array having a pair of radiators. The spacing of the radiators is such that one antenna array produces a positive phase backlobe and the other antenna produces a negative phase backlobe. Appropriate processing of the signals from the two antenna arrays permits exclusion of any signal received in the backlobe of the two arrays. The spacing between the radiators in one array is determined by the equation λ(0.25 +x) and the spacing between radiators in the other array is determined by the equation λ(0.25 -x) wherein λ is the wavelength of an electrical signal applied to the antenna system and x is the radiator spacing differential in wavelengths.

Multiple beam antenna array

Abstract: The multiple beam, short wave planar antenna array system, which simultaneously exhibits low loss, low side lobe levels, high efficiency, and low volume in a design affording independent control of the E and H plane radiation pattern shapes is particularly applicable in microwave radiometric systems such as airborne mapping systems. The antenna system generates symmetrical, matching narrow pencil beam sensitivity patterns by using symmetrically spaced sectorial receiver horns fed energy through a hyperbolic dielectric lens, the horn array and lens residing in a TE01 mode parallel plate guide, the lens being illuminated by signals collected by a broad wall slotted wave guide array supplied with a thin, planar sheet radome mounted on the energy receiving face of the array.

Phase controlled antenna array - uses transmitters, each with pilot control circuit with phase discriminator and adjustable phase shifter

Abstract: The antenna array has individual elements each connected to outputs of transmitters having phase adjusters for the carrier of a common transmission signal. Each transmitter has a pilot control circuit with a phase discriminator and a variable phase shifter. The latter first input receives a pilot signal, added to the transmission signal path in the IF plane and decoupled at the RF plane at the transmitter output. The second phase shifter input is supplied with a pilot signal which has been converted in the same manner in the RF plane via a pilot signal path. The output of the phase discriminator is coupled to the setting input of the phase shifter, this input being provided either in front of a converter and behind the pilot feed in the transmission signal path, or in front of the converter input for its oscillator.

Linear antenna arrays

Abstract: The linear antenna array comprises three or more element antennae which are disposed along a straight line and a feed circuit network connected to the element antennae via an inversion circuit for inverting power in opposite phases. The feed circuit network comprises a plurality of power dividers having common ports connected to respective element antennae, and split ports of a number corresponding to a binomial coefficient, phase shifters respectively connected to the split ports, and a common power divider connected to the phase shifters.

Multi-transceiver antenna

Abstract: The inventive antenna coupling system is capable of simultaneously radiating an omnidirectional signal pattern for a plurality of transmitters as well as providing a directive pattern to a receiver. An antenna array is coupled to the transmitters and receiver via a plurality of antenna couplers. Each coupler includes an antenna terminal, coupled to a corresponding antenna, a transmitter input terminal and a receiver output terminal. Multiple transmitters are coupled to the transmitter input terminals through a hybrid network array. The receiver is coupled to the receiver output terminal via a logic controlled antenna switch. The antenna couplers, which may be comprised of either high pass-low pass filters or circulators provide isolation between the transmit and receiver signals.

Broadband miniature antenna

Abstract: A broadband antenna of miniature size employs an array of dipole elements whose inner ends are connected to a pair of closely spaced parallel central conductors. Three pairs of dipole elements are disposed in a symmetrical array and extend outwardly from the central conductors. The longest pair of dipole elements are capacitively end loaded and the length of that longest pair is approximately one eighth of a wavelength at the lowest frequency in the broadband. The length of the shortest pair of dipole elements is in the range of a third to a quarter of the wavelength at the highest frequency in the broadband. The third pair of dipole elements is a half wavelength at an intermediate frequency in the broadband. At the points where their inner ends are connected to the central conductors, adjacent pairs of dipole elements are spaced apart by a distance in the range of a half to a quarter of the wavelength at the highest frequency in the broadband. To enable the antenna array to be disposed on a support that is suitable for a picture frame, the dipole elements are slanted with respect to the central conductors and the two longest pairs of dipole elements are arranged to approach convergence at their outer ends. To provide two panels, each of which can act as a frame for a picture, the support can be hinged with the hinge being disposed between the closely spaced parallel central conductors.

Collinear series-fed radio frequency antenna array

Abstract: A collinear series-fed antenna array formed from two spaced-apart electrical conductors extending parallel to one another in a longitudinal direction and having regularly spaced complementary changes in transverse dimensions along the longitudinal direction. These two shaped conductors are connected at one end to an RF transmitter or receiver and are substantially isolated from electromagnetic interaction with other unconnected electrical conductors in the immediate vicinity. The array is preferably fabricated by etching a copper laminate adhered to one side of a dielectric sheet which serves solely to support the shaped conductors etched thereon. There is no ground plane associated with these conductors and the dielectric merely serves to support the antenna elements. The whole assembly can therefore be made very thin and flexible and formed into a compact unit for storage when not in use.

Adaptive antenna array with several radiators - generates set of orthogonal, connected beams, one being weighted for receiving diagram formation

Abstract: The antenna array is intended for direction finding and has a receiving control processor for obtaining receiver signal samples from the respective space. The processor adjusts the signal weighting for maximising the signal-noise ratio of the combined output signal of the radiator array. For this purpose control loops are used for automatic weighting of the individual radiator signals. The N radiators are arranged in a specified structure and generate a set of N orthogonal beams of mutual continuity. The nth beam is weighted, in order to form a receiving diagram, related to the azimuth, or elevation angle, the unweighted individual diagram signal, and the number of radiators in the structure. The weighting factors, allocated to the radiators are given by a specified term, in order to provide the maximising of the signal-noise ratio.

MIPS Hover attachment

Abstract: An attachment is provided for aircraft, and particularly for helicopters, for use in conjunction with a microwave interference pattern sensor (MIPS) system, to sense low velocities, for example, such as are encountered when the helicopter is in a hover mode. The attachment includes an antenna array which is separated from the MIPS antenna array, and which comprises two sets of transmitting and two pairs of receiving antenna horn apertures mounted in orthogonal relationship with one another, the transmitting apertures of each set being scanned in sequence to produce a moving energy pattern which is intercepted by the receiving antenna apertures of the attachment, even though the aircraft is stationary.

Multifrequency hologram matrix and its application to a two-dimensional imaging

Abstract: The concept of a multifrequency hologram matrix is introduced and applied to a two-dimensional imaging system using a linear antenna array. The image processing is based on the coherent focusing of multifrequency beams synthesized from hologram matrices of several different frequencies. The imaging system is studied by means of a computer simulation and is shown to have a good range resolution.

Design of microstrip disk antenna arrays

Abstract: The radio frequency characteristics and design parameters for microstrip disk antenna elements and planar arrays are presented. Two C-band model arrays (an 8 element linear and an 8 by 8 planar) were designed, fabricated, and tested to demonstrate the technique of using microstrip elements for array applications. These arrays were designed with a cosine amplitude distribution.

Slotted waveguide linear array with polarisation control

Abstract: The design of an experimental dual-mode waveguide linear array antenna is described and measurements on a 10-element model are presented. The antenna comprises a `notched´ wall dual-mode waveguide containing an array of suitably located transverse/longitudinal slot pairs. Polarisation control is achieved by feeding the array through a 3 dB hybrid followed by a phase shifter.

Radiolocation system for determining the direction of incident electromagnetic waves

Abstract: An antenna array for a radiolocation system, consisting of three loop antennas in mutually orthogonal planes and three dipole antennas extending along the intersections of these planes, is scanned by a pair of synchronized multplexers sequentially connecting two receiving channels to different loops and to different dipoles in a recurrent cycle. The loop and dipole voltages concurrently appearing in the outputs of the two receiving channels are fed to an analog multiplier; the resulting product, after filtering and integration, is converted to digital form and written into a memory stage assigned to the respective loop/dipole combination. The registered products are sequentially read out, in the rhythm of the scan, and are processed in a digital calculator to yield azimuthal and/or elevational data which are stored and visually displayed.

Directional receiver antenna array - has two individual antennae which have single phase centre on reception from specified space angle

Abstract: The two antennae (A1,A2) have different directional effect and a common output circuit (C). This circuit receives the output signals of the two antennae over separate transmission paths. From certain spatial direction zero reception occurs at the output terminals (1, 1') of the output circuit. The zero reception points can be adjusted all round an increased spatial angular range. The individual antennae are so selected as to comprise a phase centre during reception from the spatial angular range preset for the assembly. Each separate transmission path contains an amplifier (E1, E2) and a control circuit (S). The control voltages of this circuit adjust the amplification coefficients for the amplifiers in both paths.

Computer Programs for Mutual Coupling in a Finite Planar Rectangular Waveguide Antenna Array.

Abstract: : A computer program is given to implement the equations derived in Technical Report TR-78-7, Mutual Coupling in a Finite Planar Rectangular Waveguide Antenna Array. The aperture dimensions can be less than or equal to the feeding waveguide dimensions. Three specific uniformly spaced array lattices are considered - linear, rectangular, and isosceles triangular. For the linear and rectangular lattice cases, the Toeplitz symmetry property of the admittance matrix is utilized to save storage space and computation time. The program consists of a main program and several subroutines which calculate both the half-space admittance and scattering matrices. The computer program is described and listed, along with sample input-output data. (Author)