Abstract: A comb limiter combiner for frequency-hopped communications includes an input signal coupler for coupling to a receiving antenna and distributing the antenna signal to a bank of input bandpass filters. The input bandpass filters have contiguous passbands that comprise the total receiver bandwidth. Each input bandpass filter is connected to a limiter having a threshold substantially equal to the limiting threshold of the receiver. Each limiter is connected to an output bandpass filter similar to the corresponding input bandpass filter to remove out-of-band intermodulation products generated by the limiter. The bank of output bandpass filters is connected to an output signal coupler for coupling to the front end of the receiver.

Abstract: The present invention has applications that include detecting color variation in a region, for example, color variations due to temperature changes in an area of ocean water, and, in a more specific application, detecting bioluminescence of certain organisms known to attach themselves to various objects. In one aspect of the invention, an acousto-optic tunable filter hyperspectral imaging system is moved across the region to collect a series of images in which each image represents the intensity of light at a different wavelength. In one embodiment, the acousto-optic tunable filter hyperspectral imaging system includes a motion platform for positioning the acousto-optic tunable filter hyperspectral imaging system over successive Y-coordinates of a region in a direction substantially parallel to a direction of motion of the motion platform.

Abstract: The electrical response phenomenon of electrostrictive polymers is used to harvest electrical power from the general movement of objects such as from human walking motion, for example. In a preferred embodiment of the invention, the polymer material is incorporated into the soles of footwear and is either full- or partial-wave rectified and then if desired converted to a direct current (DC) voltage level for suitable battery charging and the like.

Abstract: An automated system determines the minimum resolvable temperature difference of a thermal imager with respect to a background scene. The system comprises: a) a thermal energy for generating thermal signals; b) at least one pattern mask for transforming the thermal signals into thermal image signals; c) a thermal imager for detecting and transforming the thermal image signals into transformed signals; and d) a computer for determining the minimum resolvable temperature difference of the thermal imager using the transformed signals. A display coupled to the computer may be used to present the minimum resolvable temperature difference in human readable form.

Abstract: This invention describes an improved method of making electrical contact to porous silicon using intercalated conductive materials. The intercalation process may use gaseous, liquid or solid components to form conductive contacts to the silicon structures of the porous silicon. The intensity of the light emitted by porous silicon layers and devices can therefore be increased by the improved electrical interconnection between the mechanically, chemically and thermally fragile porous silicon and the device electrodes. The intercalation process uses conductive materials that interpenetrate the structures of the porous silicon thereby providing the improved electrical properties. Increasing the surface area over which electrical contact is made increases the junction area which allows increased electrical current flow across the junction. The increased electrical current flow across the junction provides an increased number of electrical charge carriers undergoing radiative recombination.

Abstract: A surface enhanced Raman scattering structure may be used for detecting analytes such as organic contaminants in air and aqueous environments, and metallic and anionic contaminants in water. The structure is fabricated by etching a surface of a glass substrate to form a roughened surface; creating an adhesion layer on the roughtened surface; forming metal islands, such as gold, silver, or copper, on the adhesion layer to create a composite structure; and placing the composite structure in a thiol solution to form a self-assembled monolayer over the metal islands. The thiol solution is selected to attract an analyte of interest. The roughened surface enhances the SERS response of the structure and preferably has an average surface roughness that does not exceed about 2500 Å and a periodicity that does not exceed about 12.5 microns.

Abstract: A solid state modulated ultraviolet laser comprises a laser diode for generating modulated optical energy, a waveguide upconversion laser for converting a portion of the modulated optical energy to upconversion optical energy, and a waveguide sum frequency generator for combining the modulated optical energy and the upconversion optical energy to generate a modulated ultraviolet signal.

Abstract: A method for fabricating complementary vertical bipolar junction transistors of silicon-on-sapphire in fewer steps than required for true complimentary vertical bipolar junction transistors is disclosed. Initially a thin layer of silicon is grown on a sapphire substrate. The silicon is improved using double solid phase epitaxy. The silicon is then patterned and implanted with P+-type and N+-type dopants. Subsequently a micrometer scale N-type layer is grown that acts as the intrinsic base for both an PNP transistor and as the collector for an NPN transistor. The extrinsic base for the NPN is then formed and the emitter, collector and ohmic contact regions are next selectively masked and implanted. Conductive metal is then formed between protecting oxide to complete the complementary vertical bipolar junction transistors.

Abstract: A photo-lithographic mask includes a flexible, optically transparent body having an optically transmissive first surface for receiving an optical signal, and a second surface opposite the first surface having grooves for internally reflecting first portions of the optical signal and for allowing second portions of the optical signal to be transmitted through the second surface when the second surface is pressed against a wafer. The body consists essentially of silicone. The grooves have a saw tooth profile that are configured at an angle that exceeds the critical angle of the silicone with respect to the direction of the incoming optical signal.

Abstract: Disclosed is an optical modulating device capable of use as a light-valve, display, optical filter or Fabry-Perot cavity, for example. The device lends itself to batch processing, and is compatible with monolithic integration with silicon, silicon-germanium, silicon-on-sapphire (SOS) or silicon-on-quartz (SOQ) advanced microelectronic technology (NMOS, PMOS and CMOS) for integrated control circuitry, electrical addressing, system interfacing, and the like. The device forgoes the complexities of liquid crystal constructions, and avoids the need to position and fix piezoelectric spacers within layers of the device. The invention includes first and second transparent layers that are disposed to oppose one another. Metallic layers are disposed upon the inwardly facing surfaces of the transparent layers and these are arranged to oppose each other. Spectral coupling layers are disposed upon the outwardly facing surfaces of the transparent layers opposite of the metallic layers.

Abstract: A method for making a self-aligned FET with an electrically active mask comprises the steps of forming a semiconductor layer on an insulating substrate, forming an electrically nonconductive oxide layer on the semiconductor layer, forming an electrically conductive metal layer on the oxide layer, patterning the metal layer and the oxide layer to form an electrically active gate on semiconductor layer, introducing dopants into the semiconductor layer to form a source region and a drain region masked by the metal gate, and illuminating the source and the drain regions with a pulsed excimer laser having a wavelength from about 150 nm to 350 nm to anneal the source region and the drain region.

Abstract: A liquid crystal array and associated drive circuitry are monolithically formed on a silicon-on-sapphire structure, and are fabricated by a method comprising the steps of: a) forming an epitaxial silicon layer on a sapphire substrate to create a silicon-on-sapphire structure; b) ion implanting the epitaxial silicon layer; c) annealing the silicon-on-sapphire structure; d) oxidizing the epitaxial silicon layer to form a silicon dioxide layer from a portion of the epitaxial silicon layer so that a thinned epitaxial silicon layer remains; e) removing the silicon dioxide layer to expose the thinned epitaxial silicon layer; f) fabricating an array of pixels from the thinned epitaxial silicon layer wherein each of the pixels includes a liquid crystal capacitor; and g) fabricating integrated circuitry from the thinned epitaxial silicon layer which is operably coupled to modulate the pixels.

Abstract: An active sonar system with improved noise-limited performance in littoral regions with reverberation. This invention solves the active sonar comb-waveform power-limitation problem by introducing for the first time a system employing a new comb waveform herein denominated the triplet-pair comb waveform. Ambient noise-limited performance of the system of this invention is superior to that of systems employing other Doppler-sensitive waveforms such as the geometric comb waveform. Reverberation-limited performance of the system of this invention is slightly inferior to that of systems employing other Doppler-sensitive waveforms but this invention eliminates much of the range ambiguity problems seen with other non-comb waveforms.

Abstract: An eye activity monitor of the present invention integrates multiple eye activity parameters and applies them to alertness models to determine the onset of operator fatigue or drowsiness in real time.

Abstract: A wideband antenna system comprises a stack of m antennas, where m is a positive integer, and m≧2. Each antenna includes: a) an electrically insulating substrate; b) opposed first and second radio frequency elements mounted to the substrate; c) a ground feed electrically connected to the first radio frequency element; d) an excitation feed electrically connected to the second radio frequency element; and e) a ground plane mounted to the substrate of the mth antenna. The radio frequency elements of each antenna collectively have a unique total area and are mounted to the electrically insulating substrate. The radio frequency elements of the ith antenna provide a ground plane for the kth antenna, where i and k are positive integers, 1≦k≦(i−1), and 2≦i≦m. The total area of the first and second radio frequency elements of the ith antenna is greater than the total area of the first and second radio frequency elements of the kth antenna.

Abstract: A Q-switched neodymium laser may be operated in the 0.9 &mgr;m [( &lgr;1)] band at relatively high gain levels. The laser uses a birefringent filter which provides selective discrimination for wavelengths near 1 &mgr;m [(&lgr;2)] and prevents parasitic lasing in that wavelength region. The filter includes a specific wavelength dependent crystal quartz wave plate in combination with a linear polarizer. The linear polarizer is placed between two mirrors which define a laser cavity. The wave plate provides exactly 2 full waves of retardation at the desired wavelength &lgr;1 in the 0.9 &mgr;m band, and exactly 1.75 waves of retardation at wavelength &lgr;2 near the center of the 1 &mgr;m band for one pass. A Q-switching device such as a Pockels cell is positioned in the laser cavity to selectively control a pulsed emission at &lgr;1.

Abstract: A method for fabricating a monolithically integrated liquid crystal array display and control circuitry on a silicon-on-sapphire structure comprises the steps of: a) forming an epitaxial silicon layer on a sapphire substrate to create a silicon-on-sapphire structure; b) ion implanting the epitaxial silicon layer; c) annealing the silicon-on sapphire structure; d) oxidizing the epitaxial silicon layer to form a silicon dioxide layer from portion of the epitaxial silicon layer so that a thinned epitaxial silicon layer remains; e) removing the silicon dioxide layer to expose the thinned epitaxial silicon layer; f) fabricating an array of pixels from the thinned epitaxial silicon layer; and g) fabricating integrated circuitry from the thinned epitaxial silicon layer which is operably coupled to modulate the pixels. The thinned epitaxial silicon supports the fabrication of device quality circuitry which is used to control the operation of the pixels.

Abstract: A matched pair circulator antenna isolation circuit provides isolation between an antenna and one or more receivers and transmitters and may also be applied to other RF devices. A portion of the transmit signal is extracted by a first RF circulator and divided into two phase-inverted signals. The first phase-inverted signal is coupled through a first directional coupler to cancel most of the transmit signal present in the receive signal. The second phase-inverted signal is coupled through a second directional coupler to cancel remaining transmit signal in the output of the first directional coupler. The output of the second directional coupler is coupled to the input of the receiver.

Abstract: A radar target simulator outputs multiple video and timing signals for a selected radar type from a single computer bus card slot. Several targets including cluster targets may be simulated at conveniently selectable signal-to-noise ratios. Multiple radar types may be simulated concurrently using additional bus card slots in a single desktop computer.

Abstract: A computer implemented method is described for determining message transmission time in a time division multiple access communications network.