Showing papers by "Raytheon published in 1990"

Measurement and analysis of the indoor radio channel in the frequency domain

Abstract: Using a network analyzer, several experiments for the frequency-domain characterization of the indoor radio channel in the 0.9-1.1-GHz band are performed. In the experiments, the frequency response measurements are taken at spatially distributed locations throughout the test area by fixing the receiver in a central location and moving the transmitter to different locations. The experiments are performed in a high-rise office building and a three-story building with offices and laboratories. For each experiment, the exponent of the power-distance relationship and the statistics of the 3-dB width of the frequency correlation function are determined from the frequency-domain data. The approximation to the impulse response of the channel is obtained from the inverse Fourier transform of the frequency response. An empirical exponential relationship between the 3-dB width of the frequency correlation function and the inverse of the RMS (root mean square) delay spread of the impulse response is derived. >

Pseudomorphic HEMT having strained compensation layer

Abstract: A pseudomorphic high electron mobility transistor includes a substrate for supporting a semiconductor active region. The semiconductor active region includes a channel layer comprised of InGaAs, which when disposed over said substrate develops an intrinsic lattice tensile strain and charge donor layer comprised of a wide bandgap Group III-V material, said layer being arranged to donate charge to said channel layer. The HEMT further includes a strain compensating layer having an intrinsic lattice compressive strain which is disposed between said channel layer and said substrate. The strain compensating layer has a strain characteristic which compensates for the tensile strain in the channel layer permitting said channel layer to be grow thicker or with high In concentration prior to reaching its so-called critical thickness.

Characterization of GaAs devices by a versatile pulsed I-V measurement system

Abstract: The authors build and utilized a pulsed I-V system which is capable of reaching any current-voltage point of three-terminal devices from any arbitrarily chosen DC bias point. The system, which can be used on wafer, serves as an invaluable tool for device modeling and process diagnostics. Direct dependence of the pulsed I-V curves on the DC bias was found in GaAs MESFETs and HEMTs (high-electron mobility transistors). >

Saw device and method of manufacture

Abstract: A SAW oscillator circuit including a housing having disposed therein a surface wave propagation supporting substrate with a pair of transducers coupled by surface waves propagating through the substrate and electronic circuitry connected to the pair of transducers and arranged to provide, with the connected resonator, the SAW oscillator circuit. A weight is attached to the resonator. The housing is susceptible of vibratory deflections which induce vibratory deflections in the substrate and the weight suppresses the vibratory deflections induced in the substrate of the resonator. With such arrangement, while sufficiently thick externally mounted stiffeners are not used because of space limitations, the effects of vibratory deflections induced in the substrate of the insufficiently thick, or un-stiffened housing are compensated by the weight attached to the resonator.

Doppler spread measurements of indoor radio channel

Abstract: The temporal variations caused by human movement or human-induced motion of the communication equipment, on the otherwise static indoor radio channel, are measured. For the reported narrowband measurements, a maximum Doppler spread of 6.1 Hz and a maximum RMS Doppler bandwidth of 0.87 Hz are observed.

Gaussian beam analysis of propagation from an extended plane aperture distribution through dielectric layers. I. Plane layer

Abstract: High-frequency propagation of electromagnetic wavefields from an extended planar aperture distribution through a complicated environment is addressed. Geometric optical ray tracing provides a versatile approximate approach to the class of problems, but it fails in transition regions surrounding shadow boundaries and caustics. The uniformity required there can be established by field tracking with Gaussian beams. The basic theory is summarized and applied to the two-dimensional test problem of transmission of radiation from a finite one-dimensional plane aperture through a planar dielectric layer. For a truncated uniform or focused aperture illumination, tracking the edge or caustic transition regions through the layer when it is located within the Fresnel zone of the aperture poses a problem of substantial complexity. It is shown that narrow-waisted beams, which can be propagated in their far zone as complex ray fields, reconstruct the correct transmitted field in these cases, as established independently by numerical evaluation of an exact spectral integral. >

Losses in GaAs microstrip

Abstract: Newly measured data for the loss of microstrip on 4 mil GaAs from DC to 40 GHz are presented. These data were taken from transmission measurements of lightly coupled, multiple-half-wave-length resonators. A comparison of the loss data with the predicted losses from three popular CAE (computer-aided engineering) tools is provided. The loss models provided by two out of three software vendors agree fairly well with measured data through 40 GHz. Since the measured loss roughly follows a square-law frequency relationship through 20 GHz, it should be possible to adjust the loss below this frequency and above 1 GHz by modifying the resistivity of the conductor in the simulator. >

Microstrip antenna with parasitic elements

Abstract: In a guided missile, a microstrip antenna, including a patch radiator with parasitic elements, flush-mounted and conforming to the side of the missile, producing an antenna beam which is tilted in required direction for use as a link or fuse antenna is shown Parasitic elements are used to direct the beam away from the antenna normal to the desired direction

Optical distortion coefficients of high-power laser windows

Abstract: This paper concerns the problem of describing and evaluating thermal lensing phenomena that occur as a result of the absorption of laser light in solid windows. The aberration function expansion method is applied for deriving the two optical distortion coefficients x+ and xthat characterize the degradation in light intensity at the Gaussian focus of an initially diffraction-limited laser beam passing through a weakly absorbing stress-birefringent window. In a pulsed mode of operation, the concept of an effective optical distortion coefficient Xeff, which properly combines the coefficients x+ and x- in terms of potential impact on focal irradiances, then leads to the definition of a figure of merit for distortion. The theory and calculations presented in this and earlier papers provide simple analytical tools for predicting the optical performance of a windowmaterial candidate in a specific system's environment.

Two-dimensional, phased-array optical beam steerer

Abstract: An optical beam steering device for use in a single-aperture laser transceiver system provides deflection of the transmitted and received beam in two planes, while maintaining the distinctive identities, of each channel respective to their polarizations The invention utilizes four single-dimensional beam deflecting devices, two for each orthogonal linear polarization of the two transceiver channels, one of these for each steering axis In addition, a 90° polarization rotator and a quarter-wave plate are included in the arrangement of beam deflecting devices to satisfy the polarization requirements of these devices and of the transceiver channels In a preferred embodiment, the beam deflecting devices comprise liquid crystal cells functioning as variable phase retarders, each of the cells comprising a first window having a common electrode, a second window having a multiplicity of electrodes in the form of electrically isolated, parallel stripes, and a layer of liquid crystal molecules intermediate the first and second windows Means are provided for coupling a multiplicity of control signals individually between the multiplicity of stripe electrodes and the common electrode, thereby creating selectable local variations of refractive index in the liquid crystal layer

Carbon-doped base GaAs/AlGaAs heterojunction bipolar transistor grown by metalorganic chemical vapor deposition using carbon tetrachloride as a dopant source

Abstract: Carbon tetrachloride (CCl4) has been used as a carbon doping source for the base region of a GaAs/AlGaAs Npn heterojunction bipolar transistor (HBT) grown by low‐pressure metalorganic chemical vapor deposition (MOCVD). Transistors were fabricated and characterized for dc current gain, emitter‐base junction ideality factor, base contact resistance, and external base resistance. Microwave characterization by S‐parameter measurement was performed to determine the common emitter current gain and maximum available gain as a function of frequency. Transistors with the base contact area self‐aligned to a 3×10 μm emitter finger had a dc current gain as high as 50, an emitter‐base junction ideality factor of n=1.2, and a current gain cutoff frequency of ft=26 GHz. Transistors of equal emitter area without self‐alignment exhibited dc current gain as high as 86, n=1.2, and ft=20 GHz. A base contact resistance of Rc=2.85×10−6 Ω cm2 and an external base sheet resistance of Rs=533.4 Ω/⧠ were measured. These preliminary...

Bounds on performance for multiple target tracking

Abstract: A theoretical lower bound on mean-square-estimation error is derived for tracking in dense multiple-target environments. This family of bounds is computationally tractable, because it does not require computing the optimal estimate. Computational complexity can be traded for tightness of the lower bounds by varying the number of hypotheses considered. The theory can be used to study the fundamental limitations of tracking performance, as an alternative to pursuing an endless quest for better algorithms. However, for some applications, the use of the theory could show that there is substantial room for algorithmic improvement. >

Deflector for an optical beam including refractive means

Abstract: An optical beam phase shifter includes a liquid crystal cell having a common electrode (12) on a first windows and a multiplicity of parallel stripe electrodes (14) on a second window. A multiplicity of control signals are applied between the individual stripe electrodes (14) and the common electrode (12), thereby creating local variations of the refractive index of the liquid crystal molecules (13) therebetween, which variations cause differential phase shifts across the cross section of a light beam (18) incident thereon. An optically-refractive element (11), having an index of refraction greater than the index of refraction of the liquid crystal material (13), is interposed between the beam (18) and the liquid crystal material (13). The refractive element, illustratively a prism (11), increases the angle of incidence of the beam (18) entering the liquid crystal material (13), thereby increasing the beam travel distance through the liquid crystal molecules. This allows the use of a thinner layer of liquid crystal molecules, and hence, improved response time of the optical beam phase shifter to changes in the control signals, and reduced fringing effects between stripe electrodes (14).

Spatial field power combiner having offset coaxial to planar transmission line transitions

Abstract: A cylindrical multi-port combiner having a graceful degradation characteristic with a high degree of isolation (25 db) between ports and a high combining efficiency (>90°) is disclosed. A radially-spaced inner and outer conductor forms a transmission line operating in a balanced mode. Circumferentially spaced plurality of like transmission lines have inner and outer RF absorbers at the outermost regions of the spaced adjacent inner and outer conductors, respectively. A corresponding end of each transmission line in adapted to be connected to one of a corresponding number of phase-matched RF sources. The other end of each transmission line has its inner and outer conductors connected in parallel, respectively, through stepped impedance-transforming transmission lines to form one connector for connection to an output RF load. The RF field of the desired balanced mode does not extend beyond adjacent inner and outer conductors to the absorbers; whereas when a failure of a source occurs, the resulting unbalanced mode will have its field extend to the absorbers to be damped without significantly affecting the output from the remaining operative sources.

A high power 2-18 GHz T/R switch

Abstract: A high-power 2-18-GHz T/R (transmit/receive) switch monolithic microwave IC (MMIC) has been developed for use in broadband T/R modules. This switch has a power handling of better than 35 dBm (3.2 W), 8-dB higher than any previously reported broadband switch. A combination of techniques was used to yield higher power handling while preserving low loss and high isolation. These circuit techniques include an asymmetrical design of the transmit and receive arms, the use of dual-gate FETs for handling large voltages, and the use of large FET peripheries for handling large currents. The use of dual-gate FETs in place of a stack of individual FETs reduces the device area, with a resulting reduction in parasitic series inductance through the FET and in shunt capacitance from the FET to ground. Power handling is somewhat lower for the dual-gate FET than for conventional stacked FETs, since RF voltage cannot be distributed as uniformly across the gates. Offstate capacitance is higher for a dual-gate FET than for a stacked FET, since the close proximity of the elements leads to additional parasitic capacitances. >

Luminance control for cathode-ray tube having field emission cathode

Abstract: A field emission cathode for use in a cathode-ray tube (CRT) includes groups of electron emission cells that produce different degrees of luminance on the phosphor-coated CRT screen. The cells replace the conventional CRT cathode and are fabricated on a planar surface. Each cell comprises a fixed number of discrete electron emitters, and the groups comprise different numbers of cells, typically in binary relation to one another. The cell groups of are interconnected via separate drive lines; each group is activated by applying voltage to its line. Different combinations of groups may be activated to achieve different brightness intensities on the CRT screen. A cathode having fifteen cells arranged in four groups (1, 2, 4 and 8 cells) is capable of producing sixteen shades of gray.

Real-time thermal model for an oil-immersed, forced-air cooled transformer

Abstract: A thermal model for predicting the real-time temperatures of an oil-immersed, forced-air cooled transformer is presented. The model consists of a set of three differential equations that are formulated into a computer program. Equations that can be solved for the average real-time temperatures of the core and coil assembly, oil, and tank are developed. Expressions for the convection heat transfer coefficients at all internal oil-solid interfaces, equations for calculation of the incident solar radiation, and correlations for the convective cooling rate from the external tank and cooling tubes are discussed in detail. The thermal model can predict the real-time transformer temperatures for any variation in electrical loading and for any type of ambient thermal environment. Since this model is more detailed than the ANSI/NEMA equations, the results can be expected to predict the transformer temperatures more accurately. The model yielded conservative estimates of the component temperatures when compared with temperatures measured on a distribution transformer. While this test does not verify the accuracy of the model for all types of transformers under all types of loading conditions, it does give initial credibility to the accuracy of the equations and their applicability to transformer heating. >

Apparatus and method for data error detection and correction and address error detection in a memory system

Abstract: An error detection and correction apparatus and method in a memory system for performing single symbol error correction and at least double symbol error detection of data errors and single symbol error detection and at least double symbol error detection of addressing errors using a modified Reed Solomon code. A first of three parity symbols in a codeword is used to determine the value of a single symbol error, if any, over a memory word comprising data symbols and its corresponding address comprising address symbols. A second parity symbol is used to locate a single symbol error, and a third parity symbol is used to detect at least two errors in the data and address symbols. The three parity symbols are used to generate syndromes which determine if there is an error and what corrective action to take. In calculating product terms for the modified Reed Solomon code, a technique of bit padding that requires no additional memory is used to match the number of bits needed in the Reed Solomon code data symbols to the bit width of a memory chip of a memory array in the memory system.

Condensing furnace with submerged combustion

Abstract: A high efficiency furnace having a substantially continuous wet heat exchanger wherein such continuous wet operation is provided by raising the dew point of the combustion products by submerged combustion before introduction into said head exchanger. That is, a water holding reservoir is provided between the burner and the heat exchanger, and condensate flows from the heat exchanger back into the reservoir. The combustion products are drawn through the water in the reservoir by providing a partition having a submerged lower portion, and providing a pressure differential between the chambers on the two sides of the partition. The submerged passageway from one chamber to the other may preferably be a serrated bottom edge on the partition or a plurality of apertures in the partition. The pressure differential may be provided by using a combustion blower or alternatively, using an induced draft blower preferably disposed at the flue end of the heat exchanger. Also provided is a controller that continues to activate the blower for a predetermined time period after the fuel is shut off to the burner so that the heat exchanger is flushed with pure water condensate at the end of a burning cycle.

High isolation passive switch

Abstract: A radio frequency switch disposed over a substrate having ground plane conductors disposed over an opposite surface thereof is described. The switch has at least two terminals, and includes a plurality of pairs of transistors, each one of said transistors coupled between a reference potential and a common transmission line which is coupled to one of the pair of terminals. A pair of topside conductors are disposed over the substrate to couple the transistors through plated vias to a bottom ground plane conductor. The switch further includes a series connected transistor disposed between the r.f. line and a second one of the terminals of the circuit.

Gaussian beam analysis of propagation from an extended plane aperture distribution through dielectric layers. II. Circular cylindrical layer

Abstract: For pt.I see ibid., vol.38, no.10, p.1607-17 (1990). The theory developed in pt.I of this paper for transmission of fields from an extended planar aperture through a plane dielectric layer is applied to transmission from such an aperture through an arbitrarily located cylindrical dielectric layer. By the self-consistency considerations enunciated previously, it is argued that the narrow-beam algorithm for near and far zone fields is truly predictive, although no other reference solution is now available for an independent check. As in pt.I, the aperture distributions are smoothly tapered or abruptly truncated, and they may generate beam tilts and focusing in the layer or its vicinity. >

Beam steering module

Abstract: A beam steering module for rapidly applying control signals to a plurality of digital phase shifters in a phased array antenna system. The module can receive and store a plurality of phase shift commands for a plurality of phase shifters. The commands may be quickly applied to the phase shifters to rapidly steer the beam from the antenna array.

Digital MMIC/analog MMIC structures and process

Abstract: A transmit/receive module including digitally controlled analog circuits is described. The digital circuits use a logic family adapted for use with analog monolithic integrated circuits. The disclosure also describes a preferred process to provide digital and analog microwave circuits on a common semiconductor substrate.

Microwave shielding effectiveness of EC-coated dielectric slabs

Abstract: Correct formulas for the microwave shielding effectiveness (SE) of a thin metallic layer deposited on top of a dielectric slab are derived. For coatings much thinner than the skin depth, the following holds: (a) in a half-wave geometry, SE is a function of a sheet resistance only, SE (in dB)=20*log(1+188.5/R/sub s/) if R/sub s/ is in ohms per square; (b) in a quarter-wave geometry, SE (in dB)=20*log((1+ epsilon /sub r/)/(2 square root epsilon /sub r/)+188.5/( square root epsilon /sub r/R/sub s/)), where epsilon /sub r/ refers to the dielectric constant of the substrate. These formulas provide upper and lower limits for the effective shielding performance of an electroconductive coated dielectric slab. >

Monolithic lumped element networks

Abstract: An RF circuit which may be for example a high pass filter, low pass filter, phase shifter, bandpass filter, termination network, bias network, or series or parallel resonance circuit includes at least one strip conductor coiled about a region and an outer or ring strip conductor disposed about a periphery of the at least one coiled strip conductor and coupled to said at least one coiled strip conductor through a dielectric. Parasitic capacitance between the coiled conductor and outer or ring conductor provide capacitor elements for the circuit.

Method and apparatus for batch fixating tissue specimens

Abstract: Method and apparatus for chemically fixating a plurality of tissue specimens in a multimode microwave oven. The tissue specimens are loaded in respective cassettes and then placed in radial alignment in a circular container that is filled with a fixation solution. Selective microwave shields such as metal disks with central apertures are located above and below the container which is then rotated on a turntable while being exposed to microwave energy in the microwave oven cavity. The shields are selected to provide a substantially uniform microwave field within the region occupied by the cassettes so that all of the tissue specimens are consistently and uniformly fixated.

Variable acuity non-linear projection system

Abstract: The invention provides a non-linear projection system, which includes a variable acuity non-linear holographic optical element (HOE), and an apparatus for creating the HOE. The projection system comprises a computer, a light valve which projects images generated by the computer, a lens train for focusing the images projected by the light valve, an HOE for the non-linear refraction of the focused images and a hemispherical viewing screen. The system additionally provides means for maintaining the center of the projected images in alignment with center of the field of view of an observer. The variation of the pixel size and spacing created by the system matches the variation of the human visual acuity of the observer permitting a realistic view to be presented while requiring a minimum of computer data to be generated and projected. The apparatus for creating the HOE utilizes a laser beam, three lens trains and a holographic recording medium. A procedure for utilizing the apparatus to record the HOE over a large portion of its surface area is also disclosed.

Tack compounds and microwave method for repairing voids in asphalt pavement

Abstract: A method for repairing voids such as potholes in asphalt pavement by mixing a lossy microwave material in the tack used for the tack layer. The asphalt patch used to fill the pothole is relatively non-lossy so that a substantial portion of microwave energy applied to the upper surface penetrates through the asphalt patch and is absorbed in the tack layer. The heating of the tack layer is enhanced to improve the interface bond between the asphalt patch and the surface of the pothole.

Modular transmitter and antenna array system

Abstract: A module for constructing a modular transmitter is disclosed. The module contains antenna elements along the front edge of a base. RF circuitry is fabricated on both the top and the bottom sides of the base. The base contains heat pipes to carry heat away from RF circuitry. The base is made to be plugged into a mounting block which provides electrical signals to the module and acts as a sink for the heat removed by the heat pipes.

Magnetic field cancellation circuit

Abstract: A magnetic field sensing and canceling circuit for use with a cathode ray tube (CRT) has a closed loop system consisting of flux gate sensors to measure external magnetic fields and magnetic field cancellation coils around the perimeter of the faceplate of the CRT to cancel the fields and thus minimize color and positional ac image distortion. The coils are mounted on an enclosure fabricated of a high permeability material and are positioned around the perimeter of the CRT's faceplate. Four of the coils are parallel to the top, bottom, and sides of the enclosure opening and a fifth coil is wound around the enclosure adjacent the CRT faceplate. The magnetic flux gate sensors provide output signals that are functions of the detected fields. These signals control the current in the magetic field cancellation coils and thus control the cancellation fields.