Showing papers on "Phased array published in 1978"

Conformal microstrip phased array for aircraft tests with ATS-6

Abstract: The development of a novel L -band microstrip phased array for aircraft is described. The array is electronically steerable in elevation, conformal to the surface of an aircraft, 0.14-in thick, low cost in production quantities, installed without cutting large holes in the aircraft, and capable of 12-dB gain relative to right hand circular isotrope. The microstrip radiating element is described, and its operation is explained. The array design is considered in relation to ground plane curvature, grating lobes, sidelobes, beam shape and gain. A technique for obtaining 30\deg phase resolution from 3-bit phase shifters is presented. The design of simple loaded line and switched line phase shifters is reported.

Adaptive electronically steerable phased array

Abstract: An adaptive antenna system which enhances the desired signal in the output of the system while reducing the interference from signals arriving from directions other than that of the desired signal The antenna system operates in conjunction with a modulation/demodulation system for spreading and despreading the spectrum of the desired signal By a series of deterministic perturbations of phase shifters or other signal varying devices attached to the antenna elements, the system measures the effects of these perturbations: (1) on the wide-band energy in the output of the antenna, prior to spectrum despreading, and (2) on the narrow-band energy following despreading, and then adjusts the phase shifters or other signal varying devices so as to enhance the desired signal while reducing the interfering signals

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.

Coaxial phased array antenna

Abstract: Disclosed is a coaxial antenna array for communicating circularly polarized electromagnetic radiation. A pair of open ended antenna cavities is coaxially constructed and operates by excitation of linear radiation elements arranged within each of the cavities. A pair of crossed-dipole radiation devices are centered within the inner cavity and operated by means of a phase-shifting network circuit to transmit as well as receive circularly polarized radiation. Four monopole radiation devices are symmetrically arranged to operate in the outer cavity in phase quadrature by means of the phase-shifting network circuit to also both transmit and receive circularly polarized electromagnetic radiation. Combined operation of the two antenna cavities with a 180° phase differential between the fields related to the two antenna cavities provides a broad beam, relatively wide frequency bandwidth communication capability. Particular embodiments disclosed feature a generally square cavity array as well as a circular cavity array.

A self-survey technique for self-cohering of antenna systems

Abstract: A navigation technique is applied to the location of the elements of a flexible phased array. The technique also calibrates the phase reference for each array element. The system requires several beacons of known position. The effects on beamformation of beacon position errors and of phase measurement errors (owing to multipath) are predicted. The conclusions are confirmed by computer simulation and by experimental self-cohering with a flexing four-element random array.

Limited scan phased array system

Abstract: A phased array antenna system is disclosed for scanning a narrow beam over a limited angular sector with near optimum performance while using the minimum number of active elements. An input corporate feed is coupled to a "thinned" array of phase shifters. Each phase shifter is coupled to one of a plurality of lossless periodic matrix sub-array feed networks. Radiating elements are coupled in periods such as three elements per period. The output of each phase shifter is selectively coupled to the array of radiating elements within its period and to elements in adjacent periods as well. Such an array permits a plurality of overlapping main beams having low side lobes and grating lobes.

Integrated antenna aperture

Abstract: A microwave landing system employing a phased array antenna for the generation of narrow, scanning guidance beams in which broad beam antennas used for transmitting identification signals, fly-left, fly-right guidance signals and the like with broad coverage are eliminated by applying spoiling phases to the phase shifters of the array thereby broadening the beam shape of the array to a pattern substantially identical to the pattern of a broad beam antenna formerly used. The spoiling phases are applied to the array in the time slots allocated to transmission of broad beam signals and the broad beam signals are then transmitted by the array. The spoiling phases are removed from the array during the time slots allocated to transmission of narrow scanning beams and the narrow scanning beams are then transmitted by the array. Computation of spoiling phases to provide particular patterns for particular antennas is disclosed.

Fiber Optics For Radar And Data Systems

Abstract: The application of fiber optics (FO) to modern radar system design is examined This paper presents the more conventional uses of fiber optics to transmit wideband signals as well as the less common use of their stable transmission delay characteristics to form active circuit elements within a radar The stable delay characteristics of fiber optic devices are exploited in the design of such radar circuits as a high frequency oscillator, phased array antenna, precision pulse generator, AID converter, MTI system and chirp generator The capability of fiber optics to transmit wideband information over long distances is being exploited to develop a radar remoting system for control, power, status, voice and video signals Three hundred signals are time division multiplexed over seven optical fibers for a distance of 1200 feet Future development of new materials for fiber optics will permit operation at IR frequencies and lower line loss for new applications

Phased-array maintenance-monitoring system

Abstract: A system and method for monitoring the operability of a radar system having phased-array antenna system. During an initial radiation pattern, a portion of the signals radiated from each radiating element of the array (except, in general, a center element, if any) is fed to a manifold network which combines the signals received from radiating elements which are symmetrically located with respect to the center of the array so that they differ by 180° at the single manifold output. Radio-frequency energy is added to the manifold output to adjust it to approximately zero. While the radio-frequency energy added to the manifold network is maintained at this value, the phase-shift settings of pairs of radiating elements having equal amplitude-weighting are varied from the initial setting through 360°. Failures are located by correlating the phase-shift settings and the adjusted output of the manifold network.

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.

Electronic ultrasonic sector scanning apparatus and method

Abstract: An electronically scanned phased array diagnostic system for describing internal structure of a subject by the use of ultrasonic energy. The system includes a transducer unit with an array of ultrasonic energy conversion segments and control circuitry for actuating the segments to direct ultrasonic energy into the subject. Imaging circuitry is included for interpreting electrical return signals produced by the segments in response to ultrasonic echoes. The imaging circuitry includes transmission delay circuits for imposing time delays on the return signals for steering and focusing system echo reception. Each transmission delay circuit includes first and second delay elements for impressing first and second delay time components on the return signals. Each pair of the first delay elements are coupled in parallel with separate transducer elements, and serially combined with a downstream second delay element The first delay elements provide a portion of the reception steering capability. The second elements provide the remainder of the steering, and the beam focusing, delay. components. The system further includes display apparatus responsive to the delayed return signals for producing an image of the subject's internal structure.

Phased array antenna with reduced phase quantization errors

Abstract: A phased array antenna includes a coupling network which is arranged to supply signals to pairs of elements located on opposite sides of the array center with a phase difference which is an odd-integral multiple of one-half the smallest phase step of the array phase shifters. This coupling network arrangement reduces antenna beam pointing errors which arise from a phase quantization of the array phase shifters.

Beam scanning and wavelength modulation with branching waveguide stripe injection lasers

Abstract: The operation of a branching waveguide stripe‐geometry semiconductor injection laser is described. This structure produces interference fringes in the far field which are spatially scanned by electrically varying the optical phase in each leg of the branched waveguide in a manner analogous to microwave phased array radar. Moreover, the output spectral peak of the laser also varies periodically over 70 A with these electrically induced phase shifts.

Master and slave oscillator array system for very large multiline lasers

Abstract: A new system concept, a master and slave oscillator array for very large multiline lasers, is described. This system provides a solution to the optical problem associated with these lasers—efficient power extraction with good beam quality. It also permits coherent optical adaptive techniques and fast electric steering and focusing. The slave oscillators are phase-locked to the master oscillator, and their output beams are coherently recombined as in a radar phase array. Beam steering and focusing are achieved by controlling the phases of each slave oscillator. Efficient power extraction is achieved by oscillating at several selected υ-J transitions. The system is described, and its merits, potential performance, and critical technical issues are presented.

A multiple frequency array for improved diagnostic imaging

Abstract: Cost and complexity of phased array diagnostic ultrasound imaging systems is related to the number of parallel channels during both transmit and receive. If the total numberofa ctive elements within a given aperture is reduced so that fewer parallel channels are required, grating lobes may result if the spacing of elements within the array is greater than one-half wavelength. These grating lobes may produce image ambiguities in the form of multiple images and reduced dynamic range. These grating lobes can, however, be reduced if transducers of large bandwidth are utilized. A novel broadband array is described which consists of two transducer arrays of different frequencies (one at 1.5 MHz, the other at 2.5 MHz) mounted one above the other. This method of construction avoids the usual compromise between sensitivity and bandwidth. Experiments indicate a reduction of 5 dB in the off-axis response in the transmit operation when compared to a single frequency array (2.5 MHz) with similar dimensions (16 elements within a 19.7-mm aperture). The routine diagnostic utilization of this array resulted in improved image quality in terms of reduced image artifacts and improved contrast as well as better target acquisition.

Constrained feeds for limited scan arrays

Abstract: Lossless modular hybrid coupled networks are described for application to phased arrays requiring a few beamwidths of scan. The simplest example of these networks for symmetrical limited scan is easily synthesized from analytical expressions which involve one parameter-the allowed grating lobe level. Formulas and design curves are presented for engineering applications. A practical example is calculated and compared with the conventional discrete subarray approach. Worst case radiation patterns are shown to provide the desired performance. The results show that the present technique in its simplest form requires only about half the number of phase shifters, drivers, and beam steering active devices as a conventional discrete subarray system which provides the same grating lobe level.

Design of arrays for acoustic sounder antennas

Abstract: The use of an array of loudspeaker elements for an acoustic sounder antenna is discussed. The effect of variations between the phase and amplitude of individual elements in the array is investigated and measurements are compared with the predicted radiation patterns for both a 6*6 square array and a 2*12 rectangular array of re-entrant horn loudspeakers.

The performance of an iris-loaded planar phased-array antenna of rectangular waveguides with an external dielectric sheet

Abstract: A new method for calculating the performance of an iris-loaded planar phased-array antenna of rectangular waveguides is presented. The method is based upon the expansion of the tangential electric aperture field in terms of judiciously chosen functions. Also, the influence of a dielectric sheet in front of an antenna the apertures of which are loaded with inductive irises is investigated. In the experiments, a sheet with a low relative permittivity ( \epsilon_{r} = 2.3 or \epsilon_{r} = 3.5 ) is spaced in front of a space-fed planar antenna of some 850 radiating elements, and the total transmitted power of the antenna is measured as a function of frequency and scan angle. The results indicate, that both in theory and in practice, an excellent match can be achieved with a polythene sheet ( \epsilon_{r} = 2.3 ) or a Perspex sheet ( \epsilon_{r} = 3.5 ).

Principles and applications of a dynamically focused phased array real time ultrasound system.

Abstract: The physical principles and clinical applications of a high-resolution, dynamically focused phased-array real time ultrasound system are described. Advantages of the real time technique include rapid survey capability, efficient selection of an appropriate tomographic plane, identification of pulsating structures, and dynamic studies. The capabilities of a high resolution phased array with extended dynamic focusing to a range of 15-20 cm are demonstrated in vascular, abdominal, and obstetric imaging. Appropriate clinical examples showing normal and pathological anatomy are presented. Comparisons with conventional B scans are illustrated.

Phased array antenna with extinguishable phase shifters

Abstract: In a phased array antenna wherein signals are supplied to a plurality of antenna elements by a coupling network which includes digital phase shifters for varying the phase of wave energy signals supplied to the elements, there is provided apparatus for discontinuing the supply of wave energy signals to the elements through any malfunctioning phase shifter.

Spread beam computational hardware for digital beam controllers

Abstract: A spread beam computational section of a digital beam controller for an electronically controlled phased array radar includes a linear computational portion for computing a plurality of pairs of intermediate digital words corresponding to a desired spread beam radar pattern; and a non-linear computational portion for computing a spread beam phase command word from each computed pair of intermediate digital words which have been digitally rounded off. The instant disclosure is directed to apparatus which is disposed in the spread beam computational section for digitally rounding off each computed pair of intermediate digital words by adding randomly generated digital words to a residue bit portion thereof, preferably to the most significant bits of the residue bit portion. The corresponding pairs of resultant words from the additions are truncated to a primary number of bits, more significant than the residue bits, prior to being provided to the non-linear computational portion of the spread beam computational section. The randomization process embodied by the digital round off apparatus permits the computed intermediate digital words to be rounded off to fewer significant bits than that offered by other known systems while preserving the error contribution due to the round off operation within desirable limits. As a result, the non-linear computational hardware of the beam spreading computational section may be substantially reduced.

Multichannel optical correlator for radar signal processing

Abstract: A multichannel coherent optical processor for radar signals is described in which pulse compression is achieved by matched spatial filtering. The optical system can be used for phased array, linear frequency modulated pulse burst, or other radar systems. However, only its application to linear phased array signal processing is discussed in depth. From the output optical pattern, one can obtain data on the target's fine range and azimuth (for a phased array) or fine range and Doppler (for a pulse burst radar) etc.

Aperture performance of a double-ridge rectangular waveguide in a phased array

Abstract: Despite its widely recognized broad-band characteristics, the potential of a double-ridge rectangular waveguide as a phased array element has not been systematically explored. An additional benefit in using this waveguide is its reduced size which permits realization of a compact array lattice for wide angle scanning applications. A number of treatments of ridge waveguide propagation characteristics appear in the literature [1] -[5], but an analysis of the performance of a double-ridge waveguide phased array element has only recently been published [6], [7]. The results presented are based on [6], but they include additional material. The unmatched aperture performance of a rectangular ridge-guide in a number of wide-band phased arrays with quarter-hemispherical coverage, and a single narrow-band H -plane scan design are examined. A parametric study and comparison of the unmatched aperture performance of a ridged-guide element with that of a rectangular waveguide reflects the capabilities of the double ridged-guide wide-band element in a large phased array. Such parametric study reveals to the designer the active admittance of the unmatched radiating element and leads in a systematic manner to a choice of the ridge-guide geometry and array lattice, to be followed by the determination of a suitable matching structure. This approach contrasts that of [7], which concentrates on demonstrating the feasibility of broad-band matching of a particular dual ridged-element.

Element pattern of dually polarized element in infinite phased array

Abstract: Explicit relations for the pattern of both field components of a dually polarized element in an infinite phased array are established. Calculations of the radiated field are made for an infinite array of circular waveguide apertures for several lattices and scan planes. The computed results are compared with the analytically obtained patterns of an ideal element. The effect of cross polarization on the element patterns is shown for nonprincipal plane scans.

Array Dispersion Effects on Matched Filter Output for a Linear FM Signal

Abstract: The response of a matched filter to a linear FM pulse transmitted and received through a linear phased array after return from a stationary target is studied with the matched filter assumed to be matched to the undistorted pulse. The investigation is carried out for three different feed arrangements: the parallel feed, the series end-feed, and the series center-feed. The results are presented in a general manner so as to apply to an arbitrary linear array.

Dual beam line scanner for phased array applications

Abstract: A millimeter wave line scanner is disclosed providing steered fan-shaped ms from opposite faces at substantially equal angles of a semiconductor waveguide, rectangular in cross section, and having a plurality of equally spaced metallic perturbations or strips disposed on one of the two radiating sides or faces. Different angles of scan are selectively obtained by means of at least one distributed longitudinal PIN diode formed on an adjoining side of the semiconductor waveguide having electrical circuit means coupled thereto for controlling the diode's conductivity which acts to change the guide wavelength and accordingly cause a variation in radiation angle of the two equal beams radiating in opposite directions and by means coupling energy of changing frequency to the semiconductor waveguide.

Phased array antenna with reduced phase quantization error

Abstract: Phase quantization errors in a phased array antenna are reduced by providing phase control signals which approximate ideal phase functions for symmetrical pairs of elements having an average phase value which is displaced from a nominal phase quantization value by one-quarter the smallest phase step.

Solid State Transmit/Receive Module for the PAVE PAWS (AN/FPS-115) Phased Array RADAR

Abstract: The PAVE PAWS phased array RADAR (AN/FPS-115) utilized for long range detection and tracking of SLBM's is presently under construction at two sites in the U.S.A. The system utilizes a solid state transmitter and receiver. This paper will discuss the transmit-receive configuration and the transmit/receive module developed for this application. The (sub) system configuration, module requirements and description, RF power transistors and performance to date will be presented.

Ground-To-Space Optical Power Transfer

Abstract: Using laser radiation as the energy input to a rocket, it is possible to consider the transfer of large payloads economically between low initial orbits and higher energy orbits. In this paper we will discuss the results of an investigation to use a ground-based High Energy Laser (HEL) coupled to an adaptive antenna to transmit multi-megawatts of power to a satellite in low-earth orbit. Our investigation included 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. For these evaluations we developed vertical profile models of atmospheric absorption, strength of optical turbulence (CN2), wind, temperature, and other parameters necessary to calculate system performance. Our atmospheric investigations were performed for CO2, 12C18O2 isotope, CO and DF wavelengths. For all of these considerations, output antenna locations of both sea level and mountain top (3.5 km above sea level) were used. Several adaptive system concepts were evaluated with a multiple source phased array concept being selected. This system uses an adaption technique of phase locking independent laser oscillators. When both system losses and atmospheric effects were assessed, the results predicted an overall power transfer efficiency of slightly greater than 50%.