Showing papers on "Phased array published in 1977"

Phased array antenna

Abstract: An antenna system for producing from a fixed array of active antenna elements which are each omnidirectional in a plane, a sensitivity pattern that is directional in said plane and which pattern can be rotated around the array. The system consists of at least three antenna elements located at the corners of a regular polygon and are excited with substantially equal magnitudes of current that are in the same phase at two adjacent corners and different in phase by substantially 90 electrical degrees at the third corner. The antenna system further includes an electrical power dividing and phasing network as well as electrical switching means to effect proper rotation.

Phased power switching system for scanning antenna array

Abstract: A system for a phased array antenna including a set of power amplifiers for amplifying the power of a signal to be transmitted by radiating elements of the antenna. A set of hybrid couplers are connected between the power amplifiers and the radiating elements with individual ones of the hybrid couplers being cross-connected for sharing the power of each amplifier among a set of radiating elements. The coupling of power is selectively varied between the amplifiers and the radiating elements by shifting the phase of the signal applied to each power amplifier.

A scanning spot-beam satellite system

Abstract: We propose a satellite with a high gain, movable spot beam to communicate with individual earth stations time-sharing a single channel in the tdma (Time-Division Multiple Access) mode It is estimated that this approach could readily save some 20 dB in the link budget while still providing full US coverage When this 20 dB is apportioned with the objectives of reducing the earth-station antenna size, increasing the satellite capacity, and reducing transmitter power, the effects are dramatic This technique can be combined with a fixed-spot beam system serving major traffic areas This combination can provide both full area coverage as well as multiple reuse of the frequency band A tdma burst organization is proposed, and estimates of burst lengths, beam switching intervals, and buffer storage size are made for a 100-earth-station network operating on a 600 Mb/s channel A phased array antenna with each element irradiating the entire US is employed to form the movable spot-beam This provides an attractive solution even though a closed-loop beam-forming algorithm may be required It appears feasible to construct such an antenna with nearly 50-dB gain capable of forming a spot beam toward any position within the continental United States with a switching time of a few nanoseconds

Dipole phased array with capacitance plate elements to compensate for impedance variations over the scan angle

Abstract: A phased array of dipoles mounted above a ground plane and including capacitance plate elements made of conductive metal mounted at greater distances from ground plane than the dipoles to compensate for variations in impedance over the scan angle of the phase array. With appropriate choice of the dimensions of the capacitance plate, the spacing between the dipole elements and the ground plane, and the spacing between the capacitance plates and the ground plane, the variation of input impedance over the scan angle is greatly reduced for H-plane scan.

Phased array antenna control

Abstract: The present invention provides several new and useful improvements in steering and control of phased array antennas having a small number of elements, typically on the order of 5 to 17 elements. Among the improvements are increasing the number of beam steering positions, reducing the possibility of phase transients in signals received or transmitted with the antennas, and increasing control and testing capacity with respect to the antennas.

Electronic drive system and technique for ultrasonic transducer

Abstract: Side lobe suppression is optimized in an ultrasonic generator by actively driving the transducer crystal with a signal which varies in magnitude. In a preferred embodiment a phased array of annular electrodes on a transducer crystal are individually driven with voltages having a predetermined wave form. The drive voltages are produced by generating a periodic signal and thereafter modulating this signal to provide an envelope which has the desired wave form.

Stripline four port hybrid junction

Abstract: An improved directional antenna for use in an airborne vehicle is shown. The contemplated antenna includes a planar phased array of antenna elements mechanically rotatable about an, axis of rotation, the plane of such array making an acute angle with such axis. The beam from such array may be electronically scanned, within wide limits, regardless of the orientation of the phased array. Also shown is an improved constrained centerfeed for the antenna elements in each row thereof in such array, the disclosed feed incorporating a double ladder arrangement, including wideband couplers, to permit the extensive use of stripline and at the same time to allow practically independent adjustment of azimuth and elevation difference patterns when the phased array is used as an element in a monopulse system. Also shown is an improved hybrid junction for the stripline circuits used in the disclosed antenna system, such hybrid junction being adapted to couple radio frequency energy between two stripline circuits disposed in a top and bottom relationship. Such stripline circuits share a common ground conductor having a circular opening formed therethrough for coupling radio frequency energy between the circuits. The top and bottom stripline circuits have a pair of orthogonally disposed center conductors which couple to the circular opening in the common ground conductor. The top and bottom center conductors are disposed to form an angle of 45 degrees with respect to each other.

Ultrasonic phased array systems

Abstract: Ultrasonic phased array method and apparatus for the static or dynamic investigation of structures, such as organs of the body, or intra-uterine detail, wherein ultrasonic echo pulses, reflected back from a testpiece to one or a group of adjacent transducers of a linear transducer array, are converted to corresponding electric signals which are then processed to maximize the response to the echo pulses reflected from points on a predetermined axis and to minimize the response to all other echo pulses. The method is repeated using another group of transducers in the array and another predetermined axis to produce fields of video information which are focussed and then interlaced to provide an image of the testpiece at a particular instance, the method steps being repeated in rapid succession to provide a video image representative of the testpiece in real time.

A dynamically focused multiscan system

Abstract: Clinical ultrasound instruments with a linear array transducer are nowadays one of the methods which can be used to obtain real time two dimension cardiac images 1), 2), 3). Unlike mechanical sector scanners 4) and phased array sector scanners 5), linear array systems produce a rectangular cross-sectional image of the moving heart. A rectangular picture ensures a complete imaging of structures in the vicinity of the transducer as well as of structures deep inside the body.

Electronic steering of multiple nulls for circular arrays

Abstract: This letter shows that an n-element circular array can have up to n ? 1 independent zeros in the 360° range of its directional pattern and describes suitable phasing networks to steer independently these zeros. Experimental results are presented for steering two nulls with a 4-element circular array, and the significance of certain pattern-distortion terms is briefly discussed.

Linear ultrasonic array design for echosonography

Abstract: Phased‐array echosonographic systems, currently in use in medical diagnosis, employ pulses that are a few wavelengths long at the center frequency. Design of such systems requires that arrays be composed of as few elements as are consistent with acceptable resolution and low side lobes. This paper outlines the development of a model for the field of an idealized phased array. The model is an extension of elementary array theory which includes pulse parameters and beam steering. It is specialized for the generation of simple and useful directivity patterns that are applicable at point focal regions and in the farfield. The directivity‐pattern function provides the basis for a method of designing linear arrays by nonuniform element spacing. Arrays designed by this method offer advantages over uniform linear arrays because of the smaller number of elements required for given azimuthal resolution and side‐lobe level, and because of reduced element interaction.

Phased array antenna

Abstract: PURPOSE:To decrease the number of equivalent phase shifters per one element antenna, by adjusting the phase shift of an output of one element antenna out of the two element antennas corresponding to two outputs of a variable distributors and eliminating a phase shifter to be connected to an antenna. CONSTITUTION:A high frequency signal from a transmitter 4 is distributed and phase-shifted at variable distributors 8-1-8-n so as to obtain a desired phase distribution in all element antennas 1-1, 1-2-1-2n-1, 1-2n and the element antennas 1-1, 1-3-1-2n-1 of an odd number order, and phase-shifted at phase shifters 2-2, 2-4-2-2n so as to obtain a desired phase distribution in the element antennas 1-2, 1-4-1-2n of an even number order. Since the phase can be adjusted for the output of the element antennas 1-1, 1-3-1-2n-1 of an odd number order with the variable distributors 8-1-8-n, phase shifters to be connected to the element antennas can be eliminated.

A New Ultrasonic Imaging System by Using a Rotating Random Phase Disk and Power Spectral and Third Order Correlation Analysis

Abstract: A new ultrasonic imaging system which uses neither scanning of a receiver nor beam forming by a phased array is presented. The fundamental idea is the transformation of the spatial distribution of wave intensity, which is the object to be reconstructed as the image, into temporal information by using a rotating random phase disk placed just behind the object and the analyses of the signal detected by a fixed receiver placed far from the disk. It is shown that the power spectrum of the signal is the shadow of the object on the plane which includes the point detector and the plane parallel to the object plane. Moreover if the 3rd order correlation function of the signal is calculated, this value gives directly the required reconstructed image of the object, provided that a point source is placed near the obj ect. A complete system with random phase disk made of acryl and operating at 3 MHz with FFT algorithm of a mini-computer is constructed. The theoretical discussions by using spectral representation of the wave field and resolution analyses as well as reconstructed images are presented. Although most of the results have been submitted as papers in JASA, Refs. 1 and 2, comprehensive discussions are given in this article.

Real-Time Improvement of Both Lateral and Range Resolution by Optical Signal Processing

Abstract: Electronic sector scanning systems, e.g. the Electroscan1), as intended for real-time presentation of cross-sectional images of heart, brain or abdominal organs, are based on the use of a phased array.

Scanning beam navigational beacon with transmitted coherence reference signal and thinned two-dimensional phased array

Abstract: A scanning beam navigational beacon for transmission to a remote station (aircraft, for example) which measures a navigational angle therefrom. A thinned, two-dimensional main antenna array and linear reference array are provided. A single antenna element is provided at each vertical level of the array. Reference radiations are based on main array phase to allow coherent signal processing at the remote station. Azimuth frequency diversity is provided by grouping of the excited main elements and reference array elements at different frequencies, all features cooperating to minimize the effects of azimuthally displaced multipath signals which may fall inside the far-beam of elevation guidance. Thus, the effective array aperture exhibits a distributed frequency pattern in the azimuth plane.

Phased array systems

Abstract: Phased arrays serve the same purpose as multi-element switched arrays, and that is electronical fast scanning, with ultrasound.

Analysis and design of a high power laser adaptive phased array transmitter

Abstract: The feasibility of delivering substantial quantities of optical power to a satellite in low earth orbit from a ground based high energy laser (HEL) coupled to an adaptive antenna was investigated Diffraction effects, atmospheric transmission efficiency, adaptive compensation for atmospheric turbulence effects, including the servo bandwidth requirements for this correction, and the adaptive compensation for thermal blooming were examined To evaluate possible HEL sources, atmospheric investigations were performed for the CO2, (C-12)(O-18)2 isotope, CO and DF wavelengths using output antenna locations of both sea level and mountain top Results indicate that both excellent atmospheric and adaption efficiency can be obtained for mountain top operation with a micron isotope laser operating at 91 um, or a CO laser operating single line (P10) at about 50 (C-12)(O-18)2um, which was a close second in the evaluation Four adaptive power transmitter system concepts were generated and evaluated, based on overall system efficiency, reliability, size and weight, advanced technology requirements and potential cost A multiple source phased array was selected for detailed conceptual design The system uses a unique adaption technique of phase locking independent laser oscillators which allows it to be both relatively inexpensive and most reliable with a predicted overall power transfer efficiency of 53%

Self diagnostic device

Abstract: PURPOSE:To make self diagnostics easy, by testing the motion of active element of phased array radar with the circuit which combines the hybrid circuit and the comparator.

The receive voltage transmission function of a phased array antenna element

Abstract: A general method has been developed for determining the voltage response of a phased array element to an incoming electric field. The incident field may arrive from any scan angle, and mutual coupling effects are accounted for in terms of the array element active reflection coefficient. The method defines a receive voltage transmission function \bar{T}(\theta, \phi, f) as a term whose product with the incident electric field E_{i} ( \theta, \phi, f ) results in the array element voltage response. The derivation of \bar{T}(\theta, \phi, f) is obtained by treating each phased array antenna element as a receiving aperture, having an active impedance related to the mutual coupling in the array. The element effective length is formulated using an array element receive equivalent circuit, and the transmission function \bar{T}(\theta, \phi, f) is obtained using this effective length formulation. The usefulness of the transmission function for studying the response of a phased array element to particular radar signal waveforms is suggested, and an experimental evaluation of \bar{T}(\theta \phi, f) is described using mutual coupling measurements on a 37-element crossed dipole test array.

Conformal Phased Array Breadboard.

Abstract: : Flush mounted slot antenna systems on metallic cones or ogival surfaces can be inertialessly scanned in the required direction Since scanning over a wide angular region is generally desired, the radiation characteristics, including the effect of mutual coupling on the radiating elements, must be investigated before the more detailed system aspects are considered To this end, various approximation techniques have been examined for use in pattern calculations and in impedance calculations These include the approximate asymptotic approach and the equivalence principle technique The approximation techniques provide simplified computations as compared with the exact technique, and are not applicable to all conditions A combination of exact and approximation techniques is generally required to design or analyze an array The approximate asymptotic approach, which allows the separation of the diffracted field and geometrical optics fields, has been examined in detail It appears that the asymptotic representation of the Legendre function chosen for the analysis leads to divergent expressions as the mode number m is increased, and hence limits the usefulness of the asymptotic approach in the present problem The divergent nature of the asymptotic expression is verified by computed radiation patterns of several azimuthal modes A computer program is being developed to apply the equivalence principle technique to a conical surface

Procedure for tracking manoeuvring targets with a multi-purpose phased-array radar system

Abstract: This paper describes a tracking procedure for the FUCAS-experimental multi purpose phased array system. A phased array systems is always very complex. Upto this moment there are just a few systems, the results of experiments with those systems are not yet available. FUCAS is developed to acquire experience and to get insight in the problems, the posibillities and the limitations.