Showing papers on "Phased array published in 1982"

Phased array theory and technology

Abstract: This review of array antennas highlights those elements of theory and hardware that are a part of the present rapid technological growth. The growth and change in array antennas include increased emphasis on "special-purpose" array techniques such as conformal and printed circuit arrays, wide angle scanning arrays, techniques for limited sector coverage, and antennas with dramatically increased pattern control features such as low sidelobe, adaptively controlled patterns. These new topics have substantially replaced large radar arrays in the literature and constitute a major change in the technology. The paper presents a tutorial review of theoretical developments emphasizing techniques appropriate to finite arrays, but indicating parallel developments in infinite array theory, which has become the useful tool for analysis of large arrays. A brief review of the theory of ideal arrays is followed by a generalized formulation of array theory including mutual coupling effects, and is appropriate to finite or infinite arrays of arbitrary wire elements or apertures in the presence of a conducting ground screen. Some results of array tolerance theory are summarized from the literature and retained as reference throughout discussions of array component requirements and device tolerance for low sidelobe arrays. Examples from present technology include conformal and hemispherical coverage arrays, lightweight printed circuit arrays, systems for use with reflectors and lenses in limited sector coverage applications, and wide-band array techniques.

Phased array antenna employing linear scan for wide-angle arc coverage with polarization matching

Abstract: The present invention relates to an antenna arrangement which includes a polarization diplexer capable of bidirectionally directing two orthogonally polarized signals along one path in the far field of the antenna arrangement and along two separate paths in the near field for interception along at least one of the paths by an array of feed elements. The array is arranged to provide a fixed linear phase taper along one axis across the array to produce or intercept a beam squinted at an angle 90 degrees-α to the face of the array and including a signal polarized in a first direction. Phase shifting means selectively produce a linear phase taper along a second axis across the face of the array orthogonal to the first axis to cause the beam to traverse a predetermined arc in the far field of view. Polarization mismatch at the array from the diplexer is overcome by providing a single properly inclined 90 degree polarization rotator or by two properly inclined 90 degree polarization rotators depending on the direction of polarization and whether the array is a linear or a two-dimensional array.

A method for measuring amplitude and phase of each radiating element of a phased array antenna

Abstract: In the phased array system, excitation amplitudes and phases based on the design are specified for each antenna element in order to synthesize desired beam scannings and radiation patterns. However, due to fluctuations of antenna and feed network characteristics, the amplitude and phase of each antenna element deviate from the desired values. To correct these deviations, the amplitude and phase of each antenna element must be accurately measured under specific operating conditions. In this paper, we employ variable phase shifters connected to the antenna elements and measure only the amplitude variation of the composite electric field of the entire array when the phase of each element is modified. The rotating element electric field vector method in which the measured amplitude variation is numerically processed for obtaining the amplitude and phase of the particular element is theoretically discussed and experimentally tested for its usefulness. The present method can be easily attained by simply adding software to the computer-controlled phased array system.

Beam shaping using nonlinear phase distribution in a uniformly spaced array

Abstract: The method of determination of the phase distribution of a linear array of discrete sources for a specified radiation pattern and a fixed aperture amplitude function is presented. The finite series representing the array factor is transformed into an infinite series each term of which is in the form of an integral. Synthesis is carried out from asymptotic evaluation of the integral by the stationary phase method. Computed results for sector and cosecant beam are presented.

Transesophageal Phased Array for Imaging the Heart

Abstract: A 3.5 MHz phased array has been developed for imaging the heart through the esophagus. The ultrasonic probe is fitted on the distal end of an Olympus gastroscope. Transesophageal images of the heart were obtained on ten patients. This paper describes the design and realization of the phased array and presents some clinical results obtained on patients.

Lateral beam collimation of a phased array semiconductor laser

Abstract: The lateral near‐field and far‐field radiation patterns of a phase‐locked array of gain‐guided semiconductor injection lasers are studied. These lasers exhibit a lateral far‐field beam divergence full width at half‐maximum (FWHM) of 1.5° up to 200 mW of output power per facet. Greater than 60% of the laser output power is concentrated in a low divergence beam at this high optical power. Catastrophic mirror degradation of the laser occurs at ≊250–270 mW cw per facet.

Variable frequency ultrasonic system

Abstract: The ultrasonographer changes the frequency of ultrasound pulses emitted from an ultrasonic transducer as a result of adjusting the RF frequency of the transmitter burst exciting the broadband transducer; this adjustment takes place between pulse transmissions, while examining the patient. In a phased array imager utilizing baseband processing of received echo signals, the same adjustment supplies the corresponding frequency to the demodulator circuits. An alternative method of changing the system spectrum is to have a narrow bandwidth receiver whose center frequency is varied over the available bandwidth.

Surface acoustic wave propagation in a biasing electric field

Abstract: The influence of a biasing electric field on the propagation of surface acoustic waves in LiNbO3, LiTaO3, and PbTiO3 ceramic substrates is experimentally investigated. The 128° rotated Y‐cut, X‐propagating orientation of LiNbO3 shows a linear and fairly large variation of time delay with the biasing field. Fractional time delay changes greater than 0.12% have been obtained, and values up to 0.16% appear possible in SAW devices fabricated on this material. These changes in time delay are adequate to make the technique useful for several applications. Possible applications of this effect for beam steering in phased array antennas, measurement of high voltages, temperature compensation in SAW devices, and improving the efficiency of SAW convolvers are discussed.

Magnetostatic wave devices and applications (invited)

Abstract: Microwave magnetics technology is faced with two challenges: the development of an analog signal processing capability directly at microwave frequencies, and development of electronically tunable nanosecond time delays for phased array antennas. The focus is on these two problems from the point of view of magnetostatic wave (MSW) technology in thin films such as liquid phase epitaxy yttrium iron garnet. An assessment is made of MSW devices, their role in realizing wideband phased arrays, and how MSW stacks up against competing technologies. Important devices include oscillators, signal to noise enhancers, frequency separators, filters, tunable time delays, and compressive receivers. One MSW device, a simultaneous pulse separator, is now scheduled to be incorporated into an existing system. This is a first for MSW. Although it is encouraging, much work remains in the areas of materials research, dispersion control, nonuniform biasing fields, and improved theory. The largest payoff may well be in phased arr...

Focusing of a 7700-A high power phased array semiconductor laser

Abstract: A high power (200 mW/facet) phased array semiconductor injection laser consisting of multiple optically coupled 7700‐A emitters is focused to obtain over 90 mW in a single nearly diffraction limited 2.5‐μm‐diam spot. Focusing is accomplished by imaging the vertical near‐field and the lateral far‐field patterns. Such an optical system functions only when the emitters are mutually coherent, as with this device.

Microprocessor-based fiber-optic iterative optical processor.

Abstract: The design and fabrication of an iterative optical vector-matrix processor are described. Microprocessor feedback is used to produce an iterative processor capable of solving simultaneous linear equations. It also facilitates scaling and biasing of the data and the handling of bipolar and complex-valued data as well as correction for selected system error sources. Fiber-optic interconnections are used to improve the system's alignment and to reduce its size, weight, and errors. The design, fabrication, and performance of the system are analyzed.

Method of determining excitation of individual elements of a phase array antenna from near-field data

Abstract: A near-field data measurement technique which provides sufficient data to enable the resolution of array element characteristics which are localized within a circle having a radius less than 0.61λ is disclosed. This allows phase correction of individual array elements having spacings substantially less than 0.61λ during the alignment of a phase array in a near-field test system.

Phase locking of lasers by an injected signal.

Abstract: A scheme for scaling lasers involves using a phased array of lasers. A problem encountered in this scheme is that mirror fluctuations that are due, for example, to mechanical vibrations tend to randomize the phases between lasers in the array. An analysis is presented to determine if the effects of these fluctuations can be minimized by injection locking.

A wide-band electrically small superdirective array

Abstract: The characteristics and a design procedure for an electrically small superdirective array with a 3-to-1 pattern bandwidth are presented. Theoretical patterns are compared with measurements. Trade-offs between array size, tolerances, directivity, and signal strength are discussed.

Coaxial waveguide commutation feed network for use with a scanning circular phased array antenna

Abstract: A dominant TEM mode and a pair of spatially orthogonal TE 11 modes suitably excited at the input ports of a coaxial waveguide commutator portion of a coaxial waveguide commutation feed network are employed to generate a commutatable low-sidelobe amplitude distribution at symmetrically disposed peripheral output ports of the coaxial waveguide commutator The resulting low-sidelobe amplitude distribution can be used to feed radiating elements of an associated circular phased array antenna The coaxial waveguide commutator is configured, inter alia, with a linearly tapered inner conductor surrounded by a uniform tube outer conductor to achieve a smoother TEM-dominant mode characteristic impedance transition from the input port plane to the output port plane thereof Employment of this feed geometry, in conjunction with balanced four-port feeding of the coaxial waveguide commutator which inhibits the higher order TE modes, increases the bandwidth capability while maintaining low insertion loss

A Phased Array Antenna using Microstrip Patch Antennas

Abstract: A phased array antenna using microstrip for tne AMES (Aeronautical Maritime Engineering Satellite) airborne antenna. The phased array antenna has tested over a frequency range from 1.54 to 1.65 GHz. Scanning abilities up to +30 degrees have been verified over above the frequency range. The V.S.W.R is less than 2 to 1 over 8.4 percent bandwidth. By using the method suppressing the higher modes, the boresight axial ratio has been reduced to less than 0.8 dB.

Distributed Airborne Array Concepts

Abstract: The improvement in SNR and detection range due to distributing an antenna array throughout the airframe and skin of an aircraft is examined. SNR formulas for three system configurations are presented and compared with that of a conventional, monostatic radar. Examples given in the paper show detection range increases as large as a factor of 4. Three additional potential advantages of the distributed array are an increase in spatial signal processing capability, an improvement in azimuthal resolution, and a potential reduction in transmitter power for fixed radar Performance so as to reduce the probability of intercept.

Adaptive system for suppressing interferences from directional jammers in electronically or mechanically scanning radar

Abstract: A radar antenna with a collector of microwave energy incident along the main lobe of its radiation pattern, feeding a processor whose principal channel generates a raw output signal, is provided within the effective area of that collector with one or more ancillary radiation receivers intercepting energy from side lobes encumbered by interfering signals from directional jammers. The output signals of auxiliary channels connected to the ancillary radiation receivers are subtracted in the processor, at an intermediate-frequency level, from the raw output signal of the principal channel to produce a useful signal which is fed back to an adaptive cancellation loop in each of these auxiliary channels. The collector may be an electronically scanning phased array of elemental radiators, in which case the ancillary receivers are formed by respective subgroups of some of these radiators; alternatively, the collector could be a mechanically scanning reflector provided with apertures accommodating the ancillary radiation receivers.

An adaptive system for the attenuation of an intentional disturbance applied to a phased array type radar with mechanical scanning

Abstract: 57 System for the cancellation of directional disturbances (jammers) by means of processing the signals received from the radiating elements of a phased array radar planar antenna. For the formation of the radiating beam in a certain direction all the radiating elements are not combined amongst themselves; some of these are combined separately in order to form auxiliary beams that allow the estimation of the disturbance which is present in the main beam and its removal from it. The system according to the invention does not therefore require the placement of auxiliary antennas around the main antenna and, much less, the use of multiple processing channels in the case when it is desired to control in amplitude and phase all the elementary radiators of the phased array. The signal coming from the main channel, with the effects of the disturbance removed can be further processed with the usual techniques that are used with radar receivers to detect the presence of targets and evaluate their kinematic parameters.

Phase Synchronizing a Nonrigid, Distributed, Transmit-Receive Radar Antenna Array

Abstract: A means is described for self-organizing a nonrigid, distributed, transmit-receive antenna array for use in airborne radar. The techniques are applicable to ground-based or shipborne radar as well. Methods are described for initializing the array using various primary microwave illuninators. The description of phase conjugation techniques and means for distributing phase reference to all elements in the array are the central parts of the paper.

Scanning phased array antenna system

Abstract: The present invention relates to a phased array antenna system which transmits a local oscillator signal in a scanable spotbeam from a first array of feed elements (12 l -12 m ) via a reflector or lens (16) and a frequency diplexing means (18) to a second array of feed elements (20 l -20 n ) disposed on the image plane of the first array of feed elements. A message signal in a second beam also impinging the frequency diplexing means from a separate direction is also received at the second array of feed elements. The message signal and the local oscillator signal concurrently received at each of the feed elements of the second array are mixed in individual mixers and the output of each mixer can be reradiated for transmission to a remote receiver or combined with the outputs of the other mixers for use by a local receiver. A feed element for use in an antenna for mixing a local oscillator and RF signal to produce an IF or baseband signal, or vice versa, using a stripline arrangement is also disclosed.

Compact scanning beam antenna feed arrangement

Abstract: The present invention relates to a feed arrangement for use with compact scanning beam antennas which comprises a linear phased array of small feed elements (10) which form an approximate line source that radiates a wedge-shaped cylindrical beam toward a subreflector (12) which is shaped to focus the wedge-shaped cylindrical beam to a point source which then produces a spherical wavefront. The spherical wavefront can then be focused by a main reflector (14) into linear scanning beams if desired. Multiple linear phased arrays of small feed elements can be disposed parallel to each other to form a multibeam feed arrangement for producing multiple fixed or scanning spot beams.

Performance of the Multiple Mirror Telescope (MMT). VIII - MMT as an optical-infrared interferometer and phased array

Abstract: Large gains in spatial resolution have been achieved at 0.5 and 5.0 µm by operating the MMT as a two-element interferometer with a maximum baseline of 6.9 m. Measurements of the resulting Michelson fringes at 5.0 µm have determined pathlength errors within the MMT and characterized pathlength stability versus elevation angle, temperature, and perturbations of the optical elements. At 0.5 μm, a "coherent beam-combiner" has successfully reconstructed a phased entrance pupil achieving a field >5 arcsec in diameter with 15 milli-arcsec resolution. Scientific measurements have fully resolved the 0.024 arcsec diameter disk α Tau (Aldebaran); resolved the 0.1 arcsec binary, β Tau; and provided new measurements of the spectroscopic binary, α Aur (Capella). Instrument designs employing only two additional reflections in each beam have been developed to phase the entire MMT for simultaneous applications at optical and infrared wavelengths. When configured as a phased array of four or six elements, the MMT responds to the full range of spatial frequencies present in a filled 6.9 m aperture with only a small degree of redundancy. A fully phased MMT possesses significant advantages for low background infrared photometry.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Wide angle phased array dome lens antenna with a reflection/transmission switch

Abstract: An antenna assembly configured by the combination of the high forward gain of a conventional planar phased array antenna with the wide angle scanning capability of a dome antenna. The invention includes an optically fed phased array, which may be structurally configured similar to a conventional lens array, but comprises a reflection/transmission switch and an electronic phase shifter at each radiating element. The switches facilitate operation of the phased array in two distinct modes; when the switches are set for the transmission mode, the phased array operates substantially as a conventional lens array to scan a ±60° conical sector; when the switches are set for the reflection mode, the phased array behaves like a reflect array to scan an additional ±60° to ±120° sector.

Solid State Radar's Path To GaAs

Abstract: Significant advances have been achieved recently in the field of solid-state active modules. It is now possible to project improved radar system capabilities for meeting the operational requirements of the next generation aircraft. The active element phased array radar can provide an interdiction/strike aircraft with the ability 1) to terrain sense for low level flight, 2) to detect and counter both air and ground threats, and 3) to navigate and acquire targets for improved weapon delivery. The beam scanning rates and beam shape agility necessary for interleaving these functions are not achievable with conventional mechanically scanned antennas or with phase scanned passive arrays. High performance, low cost solid-state active transmit/receive modules are key to the successful implementation of an active element phased array radar (solid-state radar).