Abstract: A method and apparatus for processing the log video output of a receiver that can measure multiple time overlapped pulses on a nearly instantaneous basis. The receiver measures frequency, pulse modulation, time of arrival, amplitude, pulse width and phase difference when simultaneous pulses are present. To detect pulse parameters a given voltage threshold must be exceeded and M out of the last N data samples must fall within a given voltage window that is above the threshold voltage. Pulse detection is initiated by establishing a dynamic noise threshold that is above the random noise level. When a pulse arrives, the value of the amplitude samples are measured and when the successive differences between the amplitude samples are small enough then a pulse presence is declared. Following detection of a pulse, amplitude samples are continuously taken and processed to detect the end of the pulse or a pulse-on-pulse condition.

Abstract: A satellite-based cellular telecommunications system employing a constellation of telecommunications satellites in medium earth orbit to provide multibeam radio frequency (rf) communications links for worldwide cellular telephone service with a minimum number of satellites. The telecommunications satellites are placed in a plurality of inclined orbits about the earth at an altitude of between approximately 5600 and 10,000 nautical miles. The characteristics of the orbits, such as the number of orbits, the inclination of each orbit, the number of satellites in each orbit and the altitude of the satellites, are tailored to maximize the coverage area of the satellites and their related line-of-sight elevation angles, while minimizing propagation time delays, the number of beam-to-beam and satellite-to-satellites handovers, and the total number of satellites.

Abstract: A satellite-based cellular telecommunications system employing a constellation of telecommunications satellites in medium earth orbit to provide multibeam radio frequency (rf) communications links for worldwide cellular telephone service with a minimum number of satellites. The telecommunications satellites are placed in a plurality of inclined orbits about the earth at an altitude of between approximately 5600 and 10,000 nautical miles. The characteristics of the orbits, such as the number of orbits, the inclination of each orbit, the number of satellites in each orbit and the altitude of the satellites, are tailored to maximize the coverage area of the satellites and their related line-of-sight elevation angles, while minimizing propagation time delays, the number of beam-to-beam and satellite-to-satellite handovers, and the total number of satellites.

Abstract: A satellite-based cellular telecommunications system employing a constellation of telecommunications satellites in medium earth orbit to provide multibeam radio frequency (rf) communications links for world-wide cellular telephone service with a minimum number of satellites. The telecommunications satellites are placed in a plurality of inclined orbits about the earth at an altitude of between approximately 5600 and 10,000 nautical miles. The characteristics of the orbits, such as the number of orbits, the inclination of each orbit, the number of satellites in each orbit and the altitude of the satellites, are tailored to maximize the coverage area of the satellites and their related line-of-sight elevation angles, while minimizing propagation time delays, the number of beam-to-beam and satellite-to-satellite handovers, and the total number of satellites.

Abstract: A satellite-based cellular telecommunications system employing a constellation of telecommunications satellites in medium earth orbit to provide multibeam radio frequency (rf) communications links for worldwide cellular telephone service with a minimum number of satellites. The telecommunications satellites are placed in a plurality of inclined orbits about the earth at an altitude of between approximately 5600 and 10,000 nautical miles. The characteristics of the orbits, such as the number of orbits, the inclination of each orbit, the number of satellites in each orbit and the altitude of the satellites, are tailored to maximize the coverage area of the satellites and their related line-of-sight elevation angles, while minimizing propagation time delays, the number of beam-to-beam and satellite-to-satellites handovers, and the total number of satellites.

Abstract: Apparatus, and a corresponding method for it use, for directly modulating an optical carrier with a radio-frequency (rf) electrical signal. A semiconductor electroabsorptive modulator is operated at an optical wavelength and electrical bias voltage carefully selected to provide a near-linear electrical-to-optical transfer characteristic and to keep rf insertion loss low. Further reduction of insertion loss is achieved by use of an extremely short device, or a single quantum well device configuration, or both. Linearity is further optimized by choosing an appropriate combination of optical polarization mode, optical reflectivity of the device facets, and the number and physical properties of multiple quantum wells.

Abstract: A high-performance superconducting digital-to-analog (D/A) converter providing asynchronous high-speed, low-power D/A conversion. The high-performance superconducting D/A converter includes a double-junction superconducting quantum interference device (SQUID) voltage divider circuit, which generates a series of discrete binary voltages, and a double-junction SQUID voltage selector circuit, which selects the binary voltages in accordance with a digital input signal. The currents generated by the selected binary voltages are added together to produce an analog output current that represents the digital input.

Abstract: A highly versatile data search engine in which multiple search cells are connected together in a pipeline through which data can be streamed. Each cell has multiple registers, and corresponding registers in each cell are connected together to form the pipeline. Characters in two data streams are compared in the pipeline, a first data stream that includes a sequence of database characters and parallel sequences of associated data, and a second data stream that includes a sequence of pattern characters and parallel sequences of associated data. The parallel data sequences associated with the pattern data include coded signals that control cell operation. One of the parallel data sequences associated with the database is a sequence of character marks, which are used to indicate search starting points in the database character sequence, and which are propagated along the database character sequence as a result of successive character matches between the pattern and database characters.

Abstract: Apparatus, and a corresponding method for its use, for producing an enhanced image of a reflective target on a remote object, such as a space vehicle with which docking maneuvers are being carried out. Radiation at two separate wavelengths illuminates the target, and reflected radiation is separated by wavelength to produce two images simultaneously. Because the target is responsive to only one of the wavelengths, but reflections from other objects are received for both wavelengths, subtraction of the two images substantially removes unwanted image components resulting from reflections from objects other than the target. Producing the two images simultaneously, using two cameras, ensures that the unwanted image components are substantially the same in the two images, and can therefore be removed by subtraction during image processing.

Abstract: A laminated composite shell structure having quasi-isotropic thermal expansion and contraction characteristics and a method for its fabrication. The laminated composite shell structure includes multiple layers of overlapping strips of composite material conforming to an axisymmetric doubly-curved surface. The fibers in the multiple layers are arranged at different relative angular orientations, with the composite strips being shaped to maintain the fibers at a constant relative angular orientation throughout the shell structure.

Abstract: A superconducting infrared photodetector employing SQUID (Superconducting Quantum Interference Device) measurement of fluxon flow in thin superconducting granular films to provide sensitive, low-noise detection of infrared radiation. The superconducting infrared photodetector includes a plurality of superconducting detector elements connected in parallel or series, means for supplying a bias current to the detector elements, and a digital or analog SQUID readout circuit. Each detector element includes a thin granular film of superconducting material which forms a randomly connected array of weakly coupled superconductors. The weakly coupled superconductors promote the formation of oppositely-polarized fluxons, which are driven to opposite sides of the film when subjected to the bias current. Incident radiation causes an increase in this fluxon flow, generating a voltage change.

Abstract: An image processing system and method for performing optical signal processing including target recognition and filtering. The system is particularly useful in remote or mobile imaging processing systems where the data gathering capabilities exceed the ability of the system to transmit this data over conventional data links. The system includes a spectrometer which receives portions of an image and produces a plurality of spectra of individual pixels in the image. A light-sensitive detector receives the spectra and converts the spectra into electrical signals. A memory unit stores a predetermined matrix of coefficients, each coefficient corresponding to one wavelength of said spectral signal. A multiply and accumulate unit received one spectral signal and a corresponding matrix coefficient and adds the products to generate a spectral measure for each pixel in the image.

Abstract: A dual-wavelength laser emitter is provided for emitting a dual-wavelength laser beam. The laser emitter includes a first laser beam source for generating a first laser beam having a first frequency and a second laser beam source for generating a second laser beam having a second frequency. A beam splitter is included for combining portions of the first and second laser beams to form a dual-wavelength laser beam. The dual-wavelength laser beam is then amplified via an amplifier. A stimulated Brillouin scattering cell may be included to phase conjugate the dual-wavelength laser beam to improve the quality of the output beam. A frequency-doubling crystal may further be included for doubling the frequency of the dual-wavelength laser beam. The dual-wavelength laser emitter then emits a laser output beam as a function of the frequencies and amplitudes of the first and second laser beams.

Abstract: An improved ice penetrating arctic buoy for release from a submarine submerged under a layer of ice includes a Global Positioning System navigational processor receiver and/or a Emergency Position Information Radio Beacon and/or surveillance apparatus, an antenna for transmission and/or reception of appropriate RF frequencies, such as Global Positioning System or other R.F. frequencies found in the environment above the ice or EPIRB R.F. frequencies originating in the buoy into the environment above the ice. Convertor means converts navigational information and/or other information outputted from said Global Positioning System receiver into coded corresponding information and an on board transmitter sends such coded information acoustically or optically and/or electrically to the submarine via an underwater data link.

Abstract: A monolithically-integrated semiconductor/ superconductor infrared detector and readout circuit providing sensitive, low-noise detection of infrared radiation for high-performance focal plane array applications. The infrared detector and readout circuit includes a semiconductor infrared detector and a semiconductor/superconductor transimpedance readout amplifier fabricated directly on the infrared detector using thin-film, integrated-circuit processing techniques. A superconducting analog-to-digital (A/D) converter digitizes the detector signals in the cryogenically cooled environment of the detector before coupling the signals to the much warmer and electromagnetically noisier environment of the back-end signal processing electronics, thus reducing noise contamination.

Abstract: Electrochromic devices are applied to selected areas on a spacecraft. Radiant energy characteristics of the electrochromic devices are altered by applying appropriate electrical excitation signals to the devices to create a force on the spacecraft due to light impinging on the devices sufficient to alter the orientation thereof or maintain it under the action of external disturbance forces or torques.

Abstract: A piezoelectric actuator/sensor package and corresponding method for its fabrication, and a method of embedding a ceramic actuator/sensor in a laminated structural member, such as a graphite-epoxy laminate. A ceramic actuator/sensor, with lead wires first bonded to it, is encapsulated in a non-conductive fiber composite material, such as fiberglass cloth and epoxy, to form a package that is precured at a suitable temperature, typically room temperature. Encapsulation provides electrical insulation, good strain coupling, protection from mechanical damage, and reduction in thermal stresses, since the coefficient of thermal expansion of the encapsulating material is selected to be between those of the ceramic and the graphite-epoxy laminate. Graphite fibers may be added to the package to enhance voltage-strain performance. The package is embedded in the structural laminate and the composite structure is cured in a manner that minimizes thermally-induced stresses.

Abstract: A semiconductor-insulator-semiconductor (SIS) structure diode device for providing fast optoelectronic switching with stimulated emission. The device includes a substrate which has a buffer layer disposed on top thereof. An n-type cladding layer is disposed on top of the buffer layer. An undoped i-region is disposed on top of the buffer layer. The i-region includes at least one quantum well disposed between two waveguide layers. A lightly doped p-type cladding layer is disposed on top of the i-region. A contact layer is further disposed on top of the p-type cladding layer. First and second contact terminals are included for providing a two-terminal device. The diode advantageously provides good lasing performance, significant negative differential resistance and strong light sensitivity. In an alternate embodiment, a third terminal is connected to the undoped i-region to thereby form a three terminal device.

Abstract: A space transfer vehicle has a plurality of thrusters for maneuvering in six degrees of freedom about three orthogonal vehicle axes. The space transfer vehicle includes four box-like thruster modules which each house an identically arranged plurality of thrusters. The thrusters are selectively energized in pairs to produce torque about the three orthogonal axes with a first magnitude for maneuvering the space transfer vehicle without a payload, and of a second magnitude for maneuvering the space transfer vehicle with a payload.

Abstract: A Josephson junction and a method for its fabrication in which a laminated junction layer is formed in situ on the side edge of a base electrode contact. The laminated junction layer forms the Josephson junction of the present invention and includes an insulating or barrier layer sandwiched between a superconducting base electrode and a superconducting counter electrode. The Josephson junction is formed on the side edge of the base electrode contact to allow very small junction areas to be fabricated using conventional optical lithographic techniques, such as photolithography. The laminated junction layer is formed in situ, with the three layers of the laminated junction layer being formed successively without removing the device from the controlled atmosphere of the deposition system, to prevent contamination of the junction region.