Showing papers on "Phased array published in 1984"

Scan blindness in infinite phased arrays of printed dipoles

Abstract: A comprehensive study of infinite phased arrays of printed dipole antennas is presented, with emphasis on the scan blindness phenomenon. A rigorus and efficient moment method procedure is used to calculate the array impedance versus scan angle. Data are presented for the input reflection coefficient for various element spacings and substrate parameters. A simple theory, based on coupling from Floquet modes to surface wave modes on the substrate, is shown to predict the occurrence of scan blindness. Measurements from a waveguide simulator of a blindness condition confirm the theory.

Regional Hyperthermia with an Annular Phased Array

Abstract: An annular phased array electromagnetic (EM) radiating device has been developed to surround regions of the body with penetrating EM fields. This instrument uses synchronous fields to focus energy at the center of a body placed in the aperture. Methods for steering the deep heating patterns have also been demonstrated and evaluated, as well as a minimally perturbing electric field (E-field) sensor to monitor the strength of the EM fields outside the body.

Optical Processor For Phased-Array Antenna Beam Formation

Abstract: The increasing need for rapid steering of antenna beams has prompted significant research and development efforts in phased-array technology. Advances in solid-state power amplification now make it possible to construct arrays with individual amplifiers at each radiating element. Consequently, the power loss in the beam-forming network is greatly reduced, since it operates in the low-power regime. Traditionally, beam-forming and steering are performed by individually controlled phase shifters and variable gain amplifiers in the signal path of each array element. Waveguide power splitters distribute the signals to the input ports of the antennas.

Analysis of inifinite phased arrays of printed dipoles

Abstract: The problem of a finite array of printed dipoles is treated, and results are presented in the form of reflection coefficient magnitudes, element patterns, and efficiency (based on power lost to surface waves). Various sized arrays are considered, and are compared with infinite array solutions. The excitation of surface waves is discussed in relation to the scan blindness phenomenon and the transition to an infinite array. Techniques for computational efficiency are also presented.

Two dimension radar system with selectable three dimension target data extraction.

Abstract: A single two dimension radar system (20) having the capability of developing two dimensional data on all targets in its surveillance volume and three dimensional data for selected targets in its surveillance volume. A single phased array antenna (23) having two selectable elevation beam patterns, a wide beam and a narrow beam, is rotated in azimuth. In the two dimension mode, targets are detected and tracked in an azimuth and range position through use of the wide elevation beam. Upon selecting a particular target in track for three dimension data extraction, the radar system changes to the three dimension mode prior to the azimuth position of the selected target, and performs a sequential lobing process of the narrow beam in elevation angle. The power ratios of the target returns in the sequential lobes are analyzed and an elevation position of the selected target is determined. The radar system reverts to the two dimension mode after leaving the azimuth position of the selected target.

An Ultrasonic Phased Array Applicator for Hyperthermia

Abstract: An ultrasonic phased array applicator for hyperthermia provides electronic steering of the sound beam rather than mechanical movement of the transducer assembly. An applicator consisting of a stack of linear phased arrays is examined. The effects of various design parameters, including individual array height and length, are discussed. work was supported in part by URI Therm-X, Inc., and in part by the National Institute of Health under NIH Training Gr-ant CA 09067. and Computer Engineering Department, University of Illinois, 1406 West Green St., Urbana, IL 61801. Manuscript received December 20,1983; revised July 17,1984. This The authors are with the Bioacoustics Research Laboratory, Electrical

Simultaneous nulling in the sum and difference patterns of a monopulse antenna

Abstract: Most adaptive array research has not directly addressed the problem of nulling in a monopulse antenna. Placing a null in the sum does not automatically place a null in the difference pattern and vice versa. Nulls may be placed in the two patterns with the use of separate adaptive weights and controls for the sum and difference channels. However, this requires two sets of adaptive hardware for one antenna. A technique for simultaneous hulling in the sum and difference channels of a monopulse phased array using one set of adaptive weights shared by both channels is described. First, the technique is described for amplitude and phase nulling, then for phase only hulling. In each case, the ability to simultaneously null in both channels with one set of variable weights is theoretically demonstrated.

Single contact tailored gain phased array of semiconductor lasers

Abstract: We demonstrate a single contact tailored gain‐guided array in which the gain profile across the array is made strongly asymmetric by varying the width of the contact stripes. A proton isolated array of six (GaAl)As lasers with 5‐μm separations and widths varying linearly between 3 and 8 μm had a single lobed far field 2° wide, close to the diffraction limit for a single supermode. Fabrication of this device is simple, and suited to large‐scale processing techniques. We also show that in such an asymmetric gain‐guided array the fundamental mode is favored over higher order modes, and that higher order modes can have single lobed far‐field patterns differing only slightly from that of the fundamental.

Adaptive nulling in monopulse antennas

Abstract: Theoretical and experimental results are presented for phase-only nulling in low-sidelobe monopulse antennas. Both results are based on a gradient search algorithm that simultaneously searches for a minimum in the sum and difference channel output powers. The array's beam steering phase shifters double as the adaptive weights. Each element in the gradient is found by changing phase shifter setting by Delta Psi (the phase shifter stepsize) and measuring the change in output power. Then the phase shifter is restored to its original value, and the process repeated for all the remaining array phase shifters. The algorithm iterates as long as each new adaptive weight setting reduces the total output power. If the output does not go down, then Delta Psi is decremented by one setting and the iteration is started again. The algorithm stops when Delta Psi =0. The adaptive weights act as random perturbations to the phase taper of the array. Consequently, the sidelobe level is proportional to the size of the phase perturbations and inversely related to the number of elements. By keeping the adaptive phase shifts small, the average sidelobe level and the main beam gain do not drastically change. >

Phased array diode lasers

Abstract: Puissance en regime continu atteignant 2,6 W. Generation de faisceaux bien collimates pour des puissances comprises entre 0,1 et 0,5 W. Couplage a des fibres optiques.

Phased-array receiver

Abstract: A phased-array receiver used in an ultrasonic diagnostic apparatus or the like for appropriately varying the phases of the output voltages from transducer elements receiving ultrasonic waves and for summing these voltages to change the directional or other characteristics of ultrasonic waves. The receiver is equipped with a plurality of blocks each comprising a tapped delay line and a crosspoint switch. The crosspoint switch is capable of selecting any desired one of various delay periods of the delay line. The receiver can perform all types of scans ranging from linear scan, intermediate scan, dynamic focusing scan, to sector scan.

Phased array transducer construction

Abstract: A method of manufacturing a phased array ultrasound transducer, and the transducer manufactured by the inventive method are described. In the method, a piezoelectric crystal is soldered to the edges of a pair of double sided printed circuit boards, each of which has traces on either side. Then, a backing material is poured to secure the crystal and boards, and a saw is used to define the elements of the transducer.

Phased array antennas with binary phase shifters

Abstract: Steerable phased array antennas of the tapered type in which the antenna ment power is maximum at the center of the array and tapers off on either side thereof. The phase shifters of each antenna element are of the binary digital type with the number of stages and hence the phase accuracy being maximum for the high power center antenna elements and tapering off on either side thereof. Redundant stages for the binary phase shifters can be provided to increase reliability.

The Use Of Optical Techniques For Beamforming In Phased Arrays

Abstract: The use of optical fibres as delay lines configured to act as a beamformer for a phased array is described. Such a beamformer operates at intermediate frequency or low microwave frequency. The relationship between operating frequency and phase accuracy in the beam-former is discussed. A detailed expression for critical system parameters of the beam-former is derived and verified with a simple experimental model operating at 120 MHz. The construction of the nodes in the beamforming network is identified as a critical feature in design on which effort needs to be concentrated.

Azimuth adaptive phased array sonar

Abstract: In ultrasonic transmission from and reception by an array probe in a phased array sonar, when an ultrasonic beam is directed substantially in front of the array probe, an ultrasonic wave having a high center frequency fo, or a bandwidth extending into higher frequencies, is transmitted and/or received in order to insure a high image resolution. When the ultrasonic beam is steered sideways, an ultrasonic wave having a lower center frequency fo, or a higher frequency range cutoff in relation to a steering angle θ, is transmitted and/or received in order to increase the angle at which grating lobes are generated and hence prevent such grating lobes from entering the angle range of the field of view.

Synthetic apertures: An Overview

Abstract: A synthetic aperture is formed when separate optical systems are combined to function as a single larger aperture. When an aperture is synthesized, independent optical systems are phased to form a common image field with resolution determined by the maximum dimension of the array and therefore exceeding that produced by any single element. In this paper, advantages and disadvantages of synthetic apertures are discussed, imaging properties are described, and implementation techniques are evaluated. Finally, some examples of existing and future phased array systems are presented.

Airplane configured with a moveable disk structure

Abstract: A delta-wing and a tapered-wing planform are combined and result in an airplane which does not require a tail assembly or a fuselage and which provides a means to resolve the conflicting requirements for large circular aperture payload space and low drag, high endurance flight. The invention consists of a flying machine with a moveable disk structure which enables a suitable circular aperture phased array antenna system to be operated either within the wing envelope or in a vertical position so that multiple narrow pencil beams can be electronically steered in opposite directions from the airplane. The location of the antenna with respect to the wing structure is such that it can operate with a corporate-fed array in the horizontal position and/or a space-fed array in the vertical position.

The MST Radar Technique

Abstract: The coherent radar technique is reviewed with special emphasis to mesosphere-stratosphere-troposphere (MST) radars operating in the VHF band. Some basic introduction to Doppler radar measurements and the radar equation is followed by an outline of the characteristics of atmospheric turbulence, viewed from the scattering and reflection processes of radar signals. Radar signal acquisition and preprocessing, namely coherent detection, digital sampling, pre-integration and coding, is briefly discussed. The data analysis is represented in terms of the correlation and spectrum analysis, yielding the essential parameters: power, signal-to-noise ratio, average and fluctuating velocity and persistency. The techniques to measure wind velocities, viz. the different modes of the Doppler method as well as the space antenna method are surveyed and the feasibilities of the MST radar interferometer technique are elucidated. A general view on the criteria to design phased array antennas is given. An outline of the hardware of a typical MST radar system is presented.

Cannon-launched projectile scanner

Abstract: An artillery shell radar system is disclosed including an antenna directed off axis to produce, in conjunction with the spin of the artillery shell, a conical scan of the target area, with the off axis angle being adjustable by changing the phase shift used in a phased array. Radiation reflected from the target after transmission by a transmitter within the artillery shell is processed to detect and select a target whose position is used to guide the artillery shell by adjustment of guide fins. Gyroscopic inertial navigation equipment and ECM detection may be included.

Cylindrical phased array antenna system to prodce wide open coverage of a wide angular sector with high directive gain and wide frequency bandwidth

Abstract: A cylindrical phased array antenna system capable of scanning at rates faster than the information rate of signals being received so that no information is lost by the scanning process, and without sensitivity loss due to sampling and with reduced frequency selectivity. The cylindrical phased array is comprised of the means to decompose the distribution of current on the radiator elements caused by wave incidence into component signals which are the Fourier spatial harmonics of the distribution, heterodyne means to differentially phase shift these component signals at rates exceeding 4 radians per cycle of the highest frequency present in the information content of the incident wave, and means to form multiple complex-weighted sums of the component signals. The sums are multiple time sequenced responses, each response corresponding to a different beam of sensitivity. The beam responses from any particular incident signal to be differentially delayed to occur in unison, and then noncoherently added, giving rise to a compressed pulse whose time of occurrence is related to the signal angle of incidence.

Phased array acoustic antenna

Abstract: A system for remote measurement of wind velocity in the atmosphere, operating from ground level. An array of acoustic transducer elements which provide for transmitting a beam of acoustic energy along a path and receiving such transmitted energy as scattered by wind in the path. The system includes signal transmitting means for driving the arrays, and signal receiving means, with a switching system for connecting the elements of the array to the transmitting means and to the receiving means, for operation as a monostatic system. Phase control for the transmitted signals comprising phase shifters and switches for selectively connecting driving signals to the elements of the array for driving selected elements at different phases to produce first, second and third beams in sequence at three different predetermined angles from a single antenna.

Array Sidelobes, Error Tolerance, Gain, and Beamwidth

Abstract: : In this report, we present a set of universal probability curves that the array error tolerance, illumination function, achievable sidelobe level, and the designed sidelobe level. We show that this set of probability curves can be used to find a lower designed sidelobe level to achieve a better error tolerance. The relations of array directivity gain and beamwidth with respect to illumination function are also discussed. These parameters can be conveniently used for this design procedure without detailed knowledge of the array illumination. Originator supplied keywords include: antenna, phased array, and array errors.

Transceiver element for phased array antenna

Abstract: A transceiver element for controlling the phase of a microwave signal passing therethrough. The transceiver element includes a plurality of switching means arranged to steer a microwave frequency signal provided by a radar system through a nonreciprocal phase shifter to a phased array antenna during a transmit mode, and to steer a microwave frequency signal received by the phased array antenna through the nonreciprocal phase shifter to the radar system during a receive mode. The microwave frequency signal passes through the phase shifter in the same direction during both the transmit and receive modes. A set of control signals is fed to such switching means and the phase shifter of the transceiver element to provide collimated and directed beams of microwave energy during the transmit mode and the receive mode.

Phased array semiconductor lasers with preferred emission in a single lobe

Abstract: A phased array semiconductor laser comprises a plurality of spatially disposed multiple lasing elements formed relative to an active region providing optical cavities and multi-emitters for light wave generation and propagation under lasing conditions. The optical field of the lasing elements are coupled into the optical cavities of adjacent lasing elements to provide a phased locked condition across the array. Structural means associated with the laser causes regions between the optical cavities to produce higher gain in those between regions as compared to the gain experienced in the optical cavities by spatially modulating the optical overlap of the optical field of each of the lasing elements laterally across the array so as to favor the fundamental supermode over the other potential supermodes of the array laser. The associated structural means may comprise a transparent waveguide layer adjacent to the active region and having a periodic undulation laterally across the laser array to provide the spatial modulation, or may comprise current confinement means to spatially modulating the current distribution laterally across the laser array to provide the spatial modulation or may comprise a combination of both types of such spatial modulation.

Phased antenna array for wind profiling applications

Abstract: A diagonal phased antenna array for use as a wind profiler by means of Doer shift measurements comprises a plurality of Yagi-Uda antennas which are oriented in a predetermined direction such that Yagi-Uda antennas have a polarization 45° offset from the principal planes of operation of the antenna array resulting in similar radiation patterns subject to a geometric taper in the array aperture with respect to the principal planes.

Feed displacement correction in a space fed lens antenna

Abstract: A space fed microwave lens antenna for deployment in outer space or other remote, hazardous or unattended location. Electronic means are provided for compensating for errors in the mechanical displacement of the phased array feed elements from the phased array lens elements.

Phase only adaptive nulling in a monopulse antenna

Abstract: A monopulse radar having a single set of phase shifters shared by both sum and difference channels. The radar utilizes an algorithm that effects simultaneous nulling in the sum and difference patterns of its phased array antenna. An algorithm is developed for phase-only nulling which does not require knowledge of the location of interference sources.

A dual band phased array using interleaved waveguides and dipoles printed on high dielectric substrate

Abstract: A dual band phased array using interleaved waveguides and dipoles has been developed. Waveguides are used for high frequency band (e.g., C-band) and printed dipoles are used for low frequency band (e.g., S-band). The dipoles are printed on Hi-K dielectric board to shorten the dipole length. The element spacings for the dipole array are equal to the element spacings of the waveguide array. This densed array environment for dipoles greatly improves impedance matching and completely eliminates the grating lobe formation for both bands.

A Concept For A Phased Array Laser Transmitter

Abstract: A concept is described for phasing the outputs of a multiple telescope array used as a laser transmitter. The technique uses samples of the transmitted beams to control optical path lengths through the separate telescopes so that the beams add coherently at the receiver. The phasing concept is applicable both to systems which provide inputs to the multiple telescopes by dividing a single laser beam and to systems in which the inputs to the telescopes and multiple, phase-locked laser beams. The approach is also compatible with single line and multi-line lasers, and it does not entail stringent alignment requirements. The concept uses a three step procedure to find the zero optical path difference condition and to effect fine control of the optical path lengths through the different telescopes. Algorithms are described for estimating the phase mismatch from focal plane measurements. The technique is susceptible to errors induced by local aberrations within the individual telescopes. The errors and one possible solution, the use of redundant measurements, are discussed. Performance requirements for a phased array laser transmitter are described.© (1984) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.