Abstract: A high speed differential optoelectronic receiver comprises a first photodetector responsive to a first incident amplitude modulated optical signal and operative to develop a first electrical signal, a second photodetector responsive to a second incident amplitude modulated optical signal that is complementary to the first optical signal and operative to develop a second electrical signal, and an amplifier having a first input that is responsive to the first electrical signal and a second input that is responsive to the second electrical signal and is operative to provide a differential output signal that is proportional to the difference between the first and the second electrical signals. Also, a method for transforming complementary amplitude modulated optical signals into a complementary electrical output signal is invented.

Abstract: Method and apparatus for spatially combining a large number of optical signals of different wavelengths carried on optical fibers (12) from laser sources (10). A dispersive optical device, disclosed as a grating (16), combines the multiple signals into a composite beam. Then a sample of the composite beam is analyzed by passing it through tunable etalon (26) and onto a sensor (30). The etalon (16) is successively tuned to passbands, each of which corresponds to the wavelength of each of the optical signals in turn. The sensor (30) measures angular deviation of each beam caused by wavelength changes, and generate control signals (on lines 36) to adjust each wavelength at its laser source. Thus the apparatus provides for reliable multiplexing of a relatively large numbers of laser sources (10), while the etalon (16) and sensor (30) operate in conjunction with a controller (32), which also generates wavelength control signals for the lasers (10), to ensure accurate beam alignment and more efficient multiplexing.

Abstract: A method for monitoring the quality of a laser process such as a laser welding process includes monitoring the light emitted from the weld plasma above the surface of the workpiece irradiated by the laser beam. The intensity of the light emitted from the plasma is compared to a predetermined value of the light emission as determined under process and workpiece conditions that produce welds of acceptable quality. Variations of the monitored light intensity greater than a preselected value can be valuated as unacceptable welds. Such variations can be caused by changes in the laser beam power, the workpiece speed, laser focusing problems, insufficient shield gas flow, workpiece deformation and weld contamination. The process monitors the light emission for a selected range of wavelengths that correspond to the major emission peaks of the light spectrum. The method enables in-process control of laser processes.

Abstract: The device and method of the invention provide a neutralizing compound that reacts with acid gases generated in laser exhaust to yield an insoluble non-toxic powder.

Abstract: A rugged and durable cover (22) for a wire rope sling (10) that encloses the length of the sling (10) and prevents particulates from being scraped from a soft nylon coating (20) of the sling (10) and enter the clean room environment of a spacecraft assembly high bay. The cover (22) is readily removable to allow the sling (10) to be visually inspected, such as is necessary during a proof load test. The cover (22) is secured to the sling (10) by a zipper type connection (48) running the length of the cover (22), and is connected to the sling (10) at both ends by straps (24), such as tie wraps. In a particular embodiment, the cover (22) is Zippertubing made of a VNH material and including a Z-track connection.

Abstract: A non-imaging laser-based tracking system for tracking the position of a targeted moving object. The tracking system includes two lasers: a reference laser and a slave laser. Each laser is a weapon, and when locked on a target, single laser effectiveness may be doubled without a thermal blooming performance loss associated with a single laser operating at twice the power. The slave laser beam is dithered relative to the reference laser beam in a direction along the longitudinal axis of the target. The system includes an optical receiver for repetitively scanning the irradiance profile reflected by the target. Since the slave laser beam is dithered relative to the reference laser beam, both laser beams will jitter and drift together providing a gain factor of two in average irradiance on the moving target.

Abstract: The invention relates to a method for producing an electrical connection to a high temperature superconductor (HTS) circuit, where a polymer material is applied to the HTS surface covering the circuit contact disposed on one surface of the HTS circuit, a via is created in the polymer material exposing the circuit contact, a diffusion barrier is applied into the via covering the circuit contact; and, a solder bump is applied to the diffusion barrier.

Abstract: Shielded stripline multi-lead flex cable is successfully attached to solder pads on a circuit board by applying a hot bar to the backside of the cable placed in abuttment with the associated solder pads. The hot bar generates sufficient heat to reflow pretinned cable elements and the corresponding solder pads of the circuit board. An attachment is attained in which the outer ground plane metal layer of the cable covers the signal lines and the other ground plane metal layer is attached adjacent those signal lines, producing effective RF shielding of the signal leads and minimizing introduction of inductance into the ground current circuit. A novel cable end configuration and cable termination is disclosed to implement the attaching procedure.

Abstract: A size-expandable and bandwidth upgradable opto-electronic circuit switch (10) and corresponding methodology for full broadcast routing of a plurality of signals with 100% non-blocking are provided. The opto-electronic circuit switch (10) includes at least two input transmitters (22) for receiving electrical input signals and for converting these electrical signals into a corresponding optical input signal, such that each optical input signal is at a different wavelength carrier. Next, a multiplexer (24) is used to combine these optical signals into a single optical input using wavelength division multiplexing, a fixed equalizer (25) provides the same gain response among all signals, and an amplifier (26) optically amplifies this optical signal received from the multiplexer. A splitter (28) receives this amplified optical signal from the amplifier (26) and transmits it as a plurality of optical output signals to at least two optical receivers (30).

Abstract: A communication system (10) implemented to be specifically matched to the time and spatially dependent statistics of a transmission channel (36). The communication system (10) is used for broadcasting over the channel (36) to users in a coverage region (18). The communication system (10) includes a transmitter (12) having an error correction encoder (30) and a weighted interleaver (32). The error correction encoder (30) includes a first input to receive data bits and a first output. The error correction encoder (30) expands each data bit received at said input by an encoder rate. The weighted interleaver (32) includes a second input to receive the expanded data bits and a second output. The weighted interleaver (32) has a non-uniform delay distribution between a minimum delay and a maximum delay to interleave the expanded data bits by the non-uniform delay distribution.

Abstract: A variable bandwidth filter that includes either a parallel or series combination of a fixed impedance, such as a capacitor, and a variable impedance, such as a variable capacitor. The series and parallel combinations enable the ideal capacitance values for the filter coupling to be approximated thereby enabling a single control voltage to control the filter bandwidth without effecting the filter's upper frequency.

Abstract: A wide dynamic range bilinear multiplier implemented with an improved Gilbert cell mixer topology linearizies the top quad core of transistors Q1, Q2, Q3 and Q4 to provide a true bilinear multiplier whose output is linearly related to both inputs over a relatively substantial input power range without the need for an additional diode predistortion circuit or increased voltage. In order to improve the linearity of the upper quad core of transistors Q1, Q2, Q3 and Q4, these transistors Q1, Q2, Q3 and Q4 are implemented as either multi-tanh doublets or multi-tanh triplets. Each multi-tanh doublet includes two pair of common emitter configured transistors Q.sub.xe and Q.sub.xae. The linear input voltage range of the multi-tanh doublets is maximized by proper selection of the emitter areas Q.sub.xae relative to Q.sub.xe, where Ae is an area factor greater than 1.

Abstract: A split power control circuit includes a solid state switch and a circuit or circuit element, such as a relatively large resistance or reactance connected between an RF signal line and ground. In order to provide relatively more precise control and thus relatively finer adjustment of the RF signal line, the RF signal line is split into a plurality of branches, with the switched control circuit or element connected to one or more of the branches. In another embodiment of the present invention, a solid state switch and serially connected circuit or circuit element, such as a resistance or reactance, are connected between an RF signal line and ground. The gate terminal of the solid state switch is capacitively coupled to the switch terminal (i.e. drain or source) connected to the RF signal line, forcing the gate bias element to become a fixed, rather than switched, load, thereby minimizing errors due to the gate biasing element and enabling tuning reactances to be used to compensate for such gate loads.

Abstract: A frequency selective medium that is adapted to receive an incident electromagnetic radiation at an angle of incidence of about 45.degree. has two arrays of conductive elements on opposite parallel surfaces (20, 22) of a dielectric substrate. In one embodiment, the conductive elements are cross-dipoles (6) each having a horizontal dipole (10) and a vertical dipole (8) of different lengths and widths. In another embodiment, the conductive elements comprise a plurality of conductive gridded rectangular loops (40). The frequency selective medium allows incident waves that are within a passband of transmit frequencies to transmit through the medium, and reflects waves at frequencies within a stopband adjacent the passband. In other embodiments, meanderline polarizers (28) are added to cross-dipole and gridded rectangular loop frequency selective media to circularly or dual-linearly polarize incident linearly polarized waves.

Abstract: A steering wheel control system (10) that employs a method for passing push-button commands from a steering wheel to a vehicle system, wherein the method is not dependant upon the contact resistance of a sliding contact (32) located in the steering wheel column. The control system (10) includes a constant current source circuit (20) that generates a unique constant current corresponding to each command. The sliding contact (32) passes the constant current between the steering wheel and the vehicle system, and a calibrated resistance circuit (40) converts the unique constant current into a discrete voltage. The discrete voltage is also converted into a digital signal for use by a microcontroller (60) to activate the vehicle systems. The use of constant currents therefore avoids operational problems associated with decreases in the overall system noise margin due to large voltage drops across the sliding contact (32).

Abstract: A complementary heterojunction field effect transistor (CHFET) in which the channels for the p-FET device and the n-FET device forming the complementary FET are formed from gallium antimonide (GaSb) or indium antimonide (InSb). An n-type HFET structure is grown, for example, by molecular beam epitaxy (MBE) in order to obtain the highest electron or hole mobility. The complementary p-type HFET is formed by p-type doping of a cap layer thereby eliminating the need for two implants for channel doping. In order to reduce the complexity of the process for making the CHFET, a common gold germanium alloy contact is used for both the p and n-type channel devices, thereby eliminating the need for separate ohmic contacts, resulting in a substantial reduction in the number of mask levels and, thus, complexity in fabricating the device.

Abstract: A space craft's rocket engines are cooled by a recirculating cooling system containing a non-propellant coolant fluid, such as water and/or ethylene glycol. With that recirculating cooling system to maintain the rocket engine combustion chamber at a lower temperature, spacecraft rocket engines may be constructed less expensively and can operate with greater safety by employing the more common metals in their construction. The cooling system also provides an easy means to warm and/or vaporize a propellant.

Abstract: A reworkable cold welded microelectronic multi-chip module contains cold welded microelectronic chips in which the chip's cold weld metal bonding pads (3) are constructed of a metal having one hardness and the corresponding cold weld metal bonding pads of the multi-chip module's substrate (5) are of a different greater hardness, which, despite the difference in hardness, cold weld to one another. Two forms of Indium preferably serve as the metals. If for any reason the chip must be removed from the module, it is found that the cold weld breaks at a predictable location. A new microelectronic chip may thereby be cold welded to the module substrate as a replacement. New rework and testing procedures are thereby made possible.

Abstract: A method of fabricating a low-inductance, in-line resistor includes the steps of: depositing a superconductive layer 12 on a base layer 14; patterning an interconnect region 16 on the superconductive layer 12; and converting the interconnect region 16 of the superconductive layer 12 to a resistor material region 18. The resistor region 18 and the superconductive layer 12 are substantially in the same plane. The method can further include the steps of depositing a conductive layer 22 on the resistor region 18 and on the photo-resist layer 20, and lifting off the photo-resist layer 20 to leave the conductive layer 22 on the resistor region 18. As such, the conductive layer 22 provides a low sheet resistivity for the resistor region 18.

Abstract: A relatively narrow fractional bandwidth saw filter formed on a standard ST cut of quartz. The electrode pattern is modified in order to eliminate distortion. In particular, the overlap pattern is formed with one or less active overlaps per wavelength in those regions of the SAW filter where the weighing function is maximum. A plurality of six finger/.lambda. electrode patterns with two active overlaps per wavelength is also provided.