Showing papers by "Raytheon published in 1972"

Rheological behavior of Sn-15 pct Pb in the crystallization range

Abstract: Rheological behavior of Sn-15 pct Pb alloy in the solidification range has been investigated using a Couette type viscometer. In samples partially solidified before shearing, deformation is localized and primarily intergranular. Samples containing more than about 0.15 fraction solid exhibit an “apparent yield point” which is on the order of 106 dyne per sq cm and increases with increasing fraction solid. When shearing is conducted continuously while the alloy is cooled from above the liquidus to the desired final fraction solid, shear stresses required for flow are reduced by about three orders of magnitude. The solid-liquid mixture now behaves as a fluid slurry. Structural examination shows that shear takes place throughout the cross section of the specimen and that the solid is present as a fine grained particulate suspension. Flow behavior can be described by a viscosity which depends on fraction solid, decreases with increasing shear rate and exhibits hysteresis when shear rate is changed. For shear rates of 200 sec−1, at 0.40 fraction solid, viscosity is about 5 poise which is equivalent to that of heavy machine oil at room temperature. The fact that the slurry is highly fluid at large fractions solid suggests potential applications in new and existing metal casting processes.

Minimum-Perimeter Polygons of Digitized Silhouettes

Abstract: The minimum-perimeter polygon of a silhouette has been shown to be a means for recognizing convex silhouettes and for smoothing the effects of digitization in silhouettes. We describe a new method of computing the minimum-perimeter polygon (MPP) of any digitized silhouette satisfying certain constraints of connectedness and smoothness, and establish the underlying theory. Such a digitized silhouette is called a ``regular complex,'' in accordance with the usage in piecewise linear topology. The method makes use of the concept of a stretched string constrained to lie in the cellular boundary of the digitized silhouette. We show that, by properly marking the virtual as well as the real vertices of an MPP, the MPP can serve as a precise representation of any regular complex, and that this representation is often an economical one.

Avalanche breakdown and the probabilistic nature of laser-induced damage

Abstract: This paper discusses the probabilistic nature of the damaging interaction between light and matter. It is shown that when one recognizes that there is some probability to induce damage at any level of optical irradiation, then the reported irreproducible damage-resistance properties of many useful materials can be understood. This point of view also explains why some optical components may be safely irradiated many times before damage occurs, though no other change in the material can be detected prior to the observation of damage. Experimental data showing the probability for surface damage as a function of power density are presented for several materials. The dependence of damage probability on optical field strength is similar to that of the dc ionization coefficients for semiconductors and gases on the applied field. This observation is discussed and it is suggested that a form of avalanche breakdown might be the cause of laser-induced damage.

Microstrip Propagation on Magnetic Substrates - Part I: Design Theory

Abstract: Formulas and graphs are presented for the effective relative permeability and the filling factors of magnetic substrates in microstrip. Both the propagation and the magnetic loss filling factors are included. In the calculation of these quantities, use was made of the filling factors for dielectric substrates obtained from Wheeler's analysis and a duality relationship between magnetic and dielectric substrates derived in this paper.

Detection Performance of the Cell Averaging LOG/CFAR Receiver

Abstract: The cell averaging LOG/CFAR receiver is a special implementation of a constant-false-alarm-rate (CFAR) receiver in which the noise level estimate is derived from a set of contiguous time samples of the output of a logarithmic (LOG) detector as obtained from a tapped delay line. This CFAR receiver is capable of operating over a larger dynamic range of noise levels than a conventional cell averaging CFAR receiver, but with somewhat poorer detectability. The performance in stationary Gaussian noise of the cell averaging LOG/CFAR receiver with no post-detection integration is determined in this paper. For a small number of reference noise samples, results were obtained by a Monte Carlo simulation using the technique of importance sampling. For a large number of reference noise samples, a second moment analysis gave the desired results. Both these results can be summarized in the following simple formula, NLOG = 1.65NLIN - 0.65, which relates the number of reference samples required by each of the two receivers for equivalent performance. Thus, for the cell averaging LOG/CFAR receiver to give the same detection performance as the conventional cell averaging CFAR receiver, the number of reference noise samples has to be increased by up to 65 percent.

High reliability system employing subelement redundancy

Abstract: A highly reliable system redundancy concept is disclosed wherein the system is divided into a number of substantially identical subelements wherein spare ones of the subelements may be substituted for failed ones of the subelements. The subelements and their corresponding loads are connected in a predetermined sequence. When one of the normally functioning subelements fails, the subelements following it in the sequence are disconnected from their corresponding loads then reconnected to the next load in the sequence. The last load in the sequence is reconnected to a spare subelement. The concept may be applied in numerous applications such as in defect tolerant computer memories, arithmetic data processing units, or in communications channel applications.

Super directive system

Abstract: A system of radiating elements arranged for forming one or more beams of radiation having radiation patterns such as a monopole, dipole, quadrupole, other multipoles or combination thereof. The individual radiating elements of the array are interconnected by circuitry providing for the summing and differencing of signals provided by adjacent radiating elements in response to incident radiation. In one embodiment the signal of one radiating element is delayed relative to the signal of an adjacent radiating element. The differencing of the signals provides for the deep nulls found in radiation patterns such as the dipole and quadrupole radiation patterns, while the delay between signals of adjacent radiating elements is adjusted for varying the shape of the directivity pattern. The system provides for varying the direction and shape of beams of the radiation pattern to provide for the detection, classification and/or tracking of a distant source of radiation as well as for illuminating a distant object. The system is responsive to the intensity of radiation received along one or more beams of the radiation pattern, and in response thereto, varies the delay between the signals of adjacent radiating elements and also provides for the selective coupling of specific radiating elements of the system.

Capacitance matrix keyboard

Abstract: An electronic system having a keyboard for entry of digitally coded data on a carrier wherein capacitive switches operated by the keyboard program a matrix which is scanned to produce digitally coded data trains.

Pulse compression radar and method of operating such a radar

Abstract: A method is described for improving the operation of a digital pulse compression radar by compensating for amplitude variations in the modulation signal of the transmitted pulse. In the disclosed embodiment, the contemplated compensation is effected by modifying the stored complex conjugate of the frequency spectrum of the transmitted waveform.

Spatially modulated imaging system

Abstract: Noncoherent radiation, such as X-rays, is spatially coded, directed through an object and spatially detected to form a spatially coded pattern, from which an image of the object may be reconstructed The X-ray source may be formed by X-ray fluorescence and subtraction of the holographic images formed by two sources having energy levels predominantly above and below the maximum absorption range of an agent in the object may be used to enhance contrast in the reproduced image Constant spatial frequency coding of the source may be used to produce a spatial carrier frequency to enhance detection of low spatial frequency components of the spatially coded pattern so that images may be a more easily reconstructed such as the optical reconstruction of spatially code formed by the off-center section of a Fresnel zone pattern by converting the detected intensity pattern to a diffraction or phase pattern

Reduced-order observers for linear discrete-time systems

Abstract: Luenberger's observer is considered as an alternate to the Kalman filter for obtaining state estimates in linear discrete-time stochastic systems. An interesting new solution to the problem of constructing optimal and suboptimal reduced-order observers is presented. The solution contains as special cases both Kalman's optimal filter and the optimal minimal-order observer of Leondes and Novak. Also, the Tse and Athans observer is obtained as a special case of the reduced-order observer solution.

Monopulse radar receiver with error correction

Abstract: A monopulse radar receiver is disclosed wherein angle error digital computation apparatus is used for correcting received target return signals in accordance with digital correction signals which are derived within such receiver in response to pilot pulses. Such digital computation apparatus includes means for generating, from pilot pulses, digital signals representative of the pair of quadrature components of video signals developed in the sum channel and each one of the difference channels. The quadrature components associated with the target return signals are then corrected in accordance with the quadrature components associated with the digital correction signals.

Strip transmission line coupler

Abstract: A coupling device for electrically connecting a strip transmission line to another transmission line, said device comprising a conductive shell having pressure means for forming electrically smooth connections with the ground planes of the strip transmission line and aperture means for permitting the center conductor of the strip transmission line to extend insulatingly into the shell, and a center pin symmetrically disposed in the shell and having means for electrically contacting the center conductor of the strip transmission line.

Microwave heating applicator

Abstract: An apparatus for and method of heating or preheating articles with microwave energy. The article is rotatably disposed within an enclosure adapted to be radiated with electromagnetic energy at 915 and/or 2450 MHz by waveguide means terminating in a radiator, such as a flared horn. The end of the radiator is shaped to conform to any article, for example, pneumatic type rubber tires having annular shaped bodies for preheating prior to vulcanization or recapping. Multimode distribution of energy within the enclosure is achieved without resort to mode stirrers. Means are disclosed for altering the displacement of the articles during heating, either vertically or angularly, to provide uniform heating across the article surface.

System for low-frequency transmission of radiant energy

Abstract: A communication system utilizing a highly directive low-frequency transmission of radiant energy which is generated by directing a beam of radiant energy at a first high frequency and at a second high frequency into a nonlinear transmission medium. By virtue of an interaction in the nonlinear medium between the energies at the first and the second high frequencies, a low frequency beam of radiation is produced having a directivity pattern comparable to that of the energy radiated at the high frequencies. The system is particularly useful for sonic examination of the seabed for sub-oceanic strata and buried objects such as pipes, in which case a receiving hydrophone and display are utilized to plot a graphical display of echoes reflected from the strata.

Compact multifrequency band antenna structure

Abstract: A compact multifrequency band antenna structure is disclosed. Such antenna structure is comprised of a first and second antenna section, each one thereof arranged to form an integral antenna structure. The first antenna section is a slotted waveguide planar array antenna (designed for operation in one frequency band) which serves as the ground plane for the second antenna section (the latter section being designed for operation in a second frequency band). The second antenna section is constructed such that the polarization of the radiation associated therewith is orthogonal to the polarization of the radiation associated with the slotted waveguide planar array antenna, thereby increasing the electrical isolation of the two antenna sections. In disclosed embodiments the second antenna section is formed from stripline and microstrip and the radiating front face portion of the slotted waveguide planar array antenna forms a ground plane for such stripline and microstrip.

Performance of a protruding-dielectric waveguide element in a phased array

Abstract: A solution for the active array reflection coefficient in a two-dimensional array of parallel-plate-guide fed protruding-dielectric elements is presented. Analysis for this class of elements is not available in the literature. Element pattern nulls are found as in the case of dielectric-slab-covered arrays. The resonance mechanisms are also shown to be similar. Bandwidth properties of this array are briefly considered. A good agreement with experiments on two small arrays is found. Departures from infinite array theory, which take the form of a ripple on the flat portion of the element patterns and dips beyond the grating lobe angle, are shown to result from the finiteness of the arrays. These edge effects may be interpreted as arising from the interference between the "space wave," i.e., the infinite array element pattern and the fields radiated by the sources induced at the array edges by a wave traveling along the array face.

Calculation of equipotentials and flux lines in axially symmetrical permanent magnet assemblies by computer

Abstract: Two equivalent theoretical models of permanent magnets are used to develop algorithms for numerically computing the magnetic scalar potential and the magnetic vector potential in the vicinity of an axially symmetric array of pole pieces and permanent magnets. A computer program based on these algorithms calculates equipotential surfaces and flux lines in and around the magnets and pole pieces. In deriving the algorithm for numerically calculating the vector potential a relationship between the magnetic scalar potential and the vector potential was found which enables the program to calculate the vector potential from the scalar potential distribution and thus generate equipotentials and flux lines with only one iterative calculation. An algorithm which calculates the scalar potential of a "floating" pole piece, that is, one on which the scalar potential has not been specified, is developed. The vector potential around the pole piece is determined from the scalar potential calculation, and this information is used to calculate the vector potential and the flux lines within the pole piece. The computer program calculates the coordinates of all points at which the equipotential lines and flux lines cross the Liebmann net. This information is fed to a cathode ray tube plotter which generates a field plot. To deal with systems in which macroscopic currents are present as well as permanent magnets, the iterative Liebmann net calculation of the vector potential is developed, and a method of applying Neumann boundary conditions to the vector potential at high-permeability surfaces is described.

Surface wave delay line structures having reduced temperature coefficient of delay time

Abstract: A surface vibratory wave system having signal coupling electrodes wherein the variation in electrical circuit characteristics is reduced by propagating surface waves through the delay medium in directions and/or in temperature ranges where the temperature coefficient of delay time between signal electrodes is substantially reduced.

Optical lens arrangement

Abstract: An improved optical lens arrangement providing arming and detonating signals for a proximity fuse is shown The illustrated lens arrangement includes a reflecting surface generally in the shape of a right circular cone, such surface effectively being faceted so that two conical detection fields are formed Also disclosed are logic and control circuits for processing optical signals from targets in either or both detection fields to differentiate between true and spurious targets

A temperature-stable bandpass filter using dielectric resonators

Abstract: A microstrip bandpass filter has been built with dielectric resonators made of a temperature-compensated material. Its unloaded Q at X band is calculated to be greater than 1200, a four-fold improvement upon conventional printed-on devices. With additional temperature compensation, a temperature coefficient less than 5 ppm/°C is shown to be feasible.

Extension of analytical design techniques to multivariable feedback control systems

Abstract: Analytical design techniques are developed for multivariable feedback control systems. The design includes a saturation constraint and provides for a disturbance at the system output and additive noise at the system input. The system inputs (signal, noise, and disturbance) are assumed to be generated by independent, stationary, stochastic processes that are adequately represented by rational power-spectral-density matrices. System elements are represented by rational transfer function matrices using the bilateral Laplace transform. The design is applicable to linear time-invariant systems. Design formulas are derived for the general case where the transfer function matrix representing the fixed elements of the system may not be square. The basic design consists of minimizing a weighted sum of the output mean-square errors and the mean-square values of a selected set of saturation signals. A variational technique is used in the optimization, and the technique of spectral factorization is used to obtain a solution. An example is presented to illustrate the design procedure.

Method and apparatus for processing eggs with microwave energy

Abstract: A method of and means for cooking and sterilizing is disclosed involving the application of microwave energy to complete processes of food products in the precooked state. Continuous transport of the product being treated is provided by means of a conveyorized system.

Radial magnetized magnet

Abstract: A permanent magnet package for electromagnetic devices, including traveling wave tubes, linear beam devices, klystrons, magnetrons, crossed field and backward wave amplifiers or oscillators and the like comprising a plurality of radially oriented linearly polarized members collectively providing a magnetic circuit. A soft iron return path between the assembled multi-segmented magnetized components completes the magnetic circuit. Magnetic materials, such as samarium-cobalt, platinumcobalt, alnico and ferrite may be utilized.

Heating element for flush top ranges

Abstract: A flush top range having replaceable heating units comprising a sandwich structure which includes a coiled heater element and heat conducting or infrared transmitting disc having a substantially planar surface, and cable means for easily connecting the unit into range circuitry with the planar surface of the disc being adapted to lie substantially in the plane of the adjoining surfaces of the range cooktop.

Fresnel zone plate imaging in radiology and nuclear medicine

Abstract: X-ray tubes and gamma ray cameras have traditionally involved trade-offs between spatial resolution and radiation flux. Recently we have shown that the use of a Fresnel zone plate as a spatially-coded source or aperture can avoid this trade-off. In radiology, this technique can eliminate the need for a rotating anode and give higher resolution, while in nuclear medicine it can be used either to decrease patient dose or exposure time, or to increase resolution and greatly simplify the apparatus. With a coded source or aperture, the image is also coded, like a hologram and can be reconstructed optically. The system is tomographic with information about all planes contained in a single film.© (1972) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Combined pitot tube and antenna

Abstract: An antenna structure for use on a jet aircraft in the VHF band is shown. The particular structure illustrated is also the housing for a Pitot tube mounted on the aircraft. Such housing is electrically insulated from the fuselage of the aircraft and capacitively coupled to a coaxial transmission line so that it may become an active antenna element without affecting the aerodynamic characteristics of the aircraft.