Abstract: A phase shifter for use in a phased array antenna includes a waveguide flange of metallic material has a narrow slot formed therein, the slot having ferroelectric material disposed uniformly therein. The slot is of reduced height relative to normal waveguide dimension, such height reduction minimizing the voltage applied across the material RF energy radiating from a source is directed to pass through the ferroelectric material. A single, thin conductive plate is disposed in the center of the slot, the plate having an electrical DC voltage imposed thereon. Such voltage creates an electric field across the material, which for a uniaxial ferroelectric orients the optic axis in a direction which is both normal to the direction of propagation of the radiation and parallel to the polarization direction of the radiation. The electric field changes the wave propagation constant (i.e., for a uniaxial ferroelectric, the extraordinary wave refractive index, n.sub.

Abstract: A signal selection system has input thereto a plurality of redundant input signals having varying values along with signals indicative of the validity of the plurality of input signals, comparison logic compares all possible pairwise combinations of the input signals to determine which input signal in each of the input signal pairs has the greater value or to determine if the input signals in each pair have equal values. Mid value selection logic determines which one or more of the values of the input signals from the plurality of valid input signals are to be used to determine the output signal according to a mid value selection criterion. The selection logic has a plurality of combinational logic elements arranged to execute predetermined Boolean logic equations in determining which one or more of the values of the input signals from the plurality of valid inputs are to be used to determine the output signal according to the predetermined mid value selection criterion.

Abstract: A method of attaching an optical fiber to an IOC includes the step of forming an alignment groove in the waveguide surface of the IOC by utilizing a laser ablation system to remove a predetermined portion of the IOC material. Next, a dicing saw or other cutting means is used to cut into the IOC at a depth less than the thickness of the IOC, the cut forming a cut surface which is normal or at an angle with respect to both an optical axis of the waveguide and to an axis of the alignment groove, such step of cutting performing the additional function of optically polishing the cut surface. Next, an optical fiber is disposed within the alignment groove, and the fiber core is optically aligned with the optical axis of the waveguide by translational and rotational positioning of the fiber end face adjacent to the cut surface.

Abstract: A transformer isolates a control circuit from a FET, the control circuit including a clock generator for providing, when enabled, a clock signal to the transformer primary. A PWM input selectively disables the clock generator from providing the clock signal to the transformer primary. The transformer secondary is connected in a full wave centertap configuration for providing a full wave rectified version of the clock signal, the full wave rectified version being a relatively constant DC voltage signal supplied at one level to the FET to turn on the FET when the clock generator is enabled to provide the clock signal to the primary. The centertap configuration provides a relatively constant DC voltage signal at a second level to the FET to turn off the FET when the clock generator is disabled by the PWM input from providing the clock signal to the primary.

Abstract: A pair of interferometers, such as Mach-Zehnders, are disposed in a series arrangement in which a signal fed to an input of the first Mach-Zehnder is modulated by an optic modulator, the modulated signal is fed to an input of the second Mach-Zehnder and is modulated by a second optic modulator, the two optic modulators effectively being connected in a series or cascade arrangement. The phase offset of both modulators and the contrast of one modulator are adjusted to minimize both second and third order harmonics inherently generated by the modulation process of each modulator, thereby providing an improved linear response in the output signal of the second Mach-Zehnder.

Abstract: An improved two-dimensional optical centroid processor ("OCP") wavefront sensor is described in which a scanning mirror 146 scans the wavefront of input light 130 to provide a scanned beam 148 (i.e. a portion of the wavefront). The scanned beam 148 is focused on an OCP 168 filter comprising four rows of mask cells. The filtered light emanating from the cells impinges on one-dimensional photodetector devices 192, 198, 202, 206 (i.e. photodetector rows). Thus, the scanning of the wavefront by the scanning mirror provides two-dimensional measurement while employing one-dimensional photodetector devices. Each of the photodetector devices provides an output to a ratio calculator 201 which is used to correct the tilt in the wavefront by driving a deformable mirror (not shown).

Abstract: A voltage reference circuit maintains two nodes at constant voltages with respect to a reference by means of a tapped divider chain in parallel with a floating voltage reference circuit, both of which feed into the output node of a single differential amplifier. The reference circuit maintains a constant voltage across the divider chain and the amplifier floats the divider up or down to maintain a node in the chain at the reference voltage.

Abstract: An SOI circuit includes a set of buried body ties that provide ohmic contact to the otherwise floating transistor bodies disposed on an insulating layer and both provide a path for holes generated by impact ionization and also act as a potential shield between the substrate potential and the transistor sources. The same fabrication technique provides a buried interconnect layer between transistors that can be employed as a mask programmable local interconnect in an ASIC such as a gate array. The process provides for independent control of differential mesa thickness and buried body tie thickness, so that fully and partially depleted transistors can be fabricated simultaneously and placed on appropriate mesas without affecting the body ties.

Abstract: An aircraft flight control system including model following control laws includes improved logic and algorithms to limit the error between a desired parameter value from the output of a model and an actual parameter value. Such logic is operable to sense the amount of said parameter error and to limit the amount of the error if it exceeds a predetermined value. The difference between the predetermined limit and the actual error is fed back to the model such that the output of the model is adjusted so that the error between the desired and actual parameter values does not exceed the predetermined value.

Abstract: Apparatus for removing heat energy of a cooling medium passing from a space suit liquid cooling garment includes a heat sink assembly for absorbing and rejecting the heat energy and a heat transfer means for transferring the heat energy of the cooling medium to the heat sink assembly. The heat transfer means, which is comprised of an array of thermoelectric modules, regulates the quantity of heat energy transferred from the cooling medium to the heat sink assembly. The heat sink assembly includes a material which isothermally changes phase while absorbing heat energy.

Abstract: In a fiber optic rotation sensor having a pair of light waves counter-propagating in an optical waveguide loop, a phase modulator is driven by a modulating signal at the loop eigenfrequency. Upon exiting the loop the waves are combined into a light intensity signal which is sensed, the sensed signal including a component in quadrature with a desired rotation rate component, the magnitude of the quadrature component being proportional to any deviations in the frequency of the modulating signal from the loop eigenfrequency. The phase modulator is servo-controlled so as to drive the quadrature component to zero, thereby compensating for any deviations in the modulator frequency from the loop eigenfrequency.

Abstract: An integrated optics (IO) chip comprising an optical signal path disposed in a principal plane of a crystalline chip having a known chip thickness, anisotropic thermal characteristics, and crystallographic orientation, is mounted to a first surface of a similar thermally anisotropic crystalline material substrate. A second surface of the substrate, spaced from the first surface at a substrate thickness approaching the known chip thickness, is bonded to a mounting surface with a visco-elastic polymer adhesive. Employing this adhesive allows a substantial reduction in the thickness of the substrate as compared to the thickness of the IO chip while allowing vibration and high G-shock loads to be imparted on the structure without affecting the electro-optical properties of the IO chip.

Abstract: An automatic control system includes a multiplier for multiplying the error signal fed to an integrator in accordance with the state of the integrator. The multiplier multiplies the error signal by a unity gain factor over the normal range of integral control; whereas, the multiplier multiplies the error signal by a factor greater than one, typically ten, when the integrator output is saturated at either the minimum or maximum values. The high multiplication value of the error signal ensures a sufficiently quick recovery from an integrator saturation condition.

Abstract: A method of aligning the optical axes of an optical fiber and a waveguide imbedded in an integrated optical chip and of attaching the fiber to the chip includes the step of coating the outer surface of the fiber with solder in the vicinity of an end of the fiber. A portion of the fiber at the coated end is cut away such that a flat surface at a tangential or near tangential relation to the fiber core results. A surface of the chip has solder pads disposed thereon such that the outer edges of the cut portion of the fiber contacts the solder pads when the flat surface of the fiber is placed in contact with the surface of the chip, such placement of the fiber onto the chip providing for vertical alignment of the optical axes of the fiber core and the waveguide in the chip.

Abstract: Parameters indicative of gas turbine engine operational characteristics are sensed and the signals processed to derive further operational characteristic information therefrom, each information signal being compared in a subroutine to a corresponding threshold signal for exceedence thereof, the magnitude of each threshold signal being indicative of incipiency of compressor stall, a counter being incremented in the subroutine upon any threshold exceedence occurrence, the amount of counter increment depending on the ability of each information signal to predict the incipiency of stall, the higher the counter value the greater the stall incipiency. The counter is decremented during each subroutine execution, the counter value during the current subroutine execution being compared to that of the previous subroutine execution to determine the direction of stall incipiency. The counter is utilized as a bias signal to an engine acceleration schedule to vary the rate of acceleration as the counter is varied.

Abstract: The existence of autorotation of a load (e.g., a helicopter rotor system) coupled to the free turbine of a gas turbine engine is determined and a signal indicative thereof enables an integrator which, upon autorotation, integrates rate-based recovery anticipation provided thereto, the integrator output providing a time-composite bias signal to the main control portion of the engine fuel control to increase the speed of the gas generator of the engine in anticipation of rotor reengagement with the free turbine. The amount of recovery error is determined from the rotor speed error and is multiplied with the integrator output, the product being fed, upon completion of autorotation recovery, to the integrator input whose output now provides a controlled removal of the bias signal from the main control portion so as to minimize transients induced therein.

Abstract: An apparatus measures torque in high accuracy, close tolerance, precision output axis suspension bearings and corresponding pivots. The bearings are received in corresponding apertures at the ends of axial aligned, rotatable test shafts. A pendulum, having an eccentric cylindrical shaped aperture for holding a pair of pivots in axial alignment, is disposed between the test shafts, the pivots being received in the bearings. The pendulum is further provided with a reflective panel; a laser light source is arranged to direct a beam of laser light onto the pendulum reflective panel, and a photosensitive position sensing array is oriented to sense a laser light beam reflected off the panel. The test shafts are rotated, and the magnitude of a deflection of the reflected laser light beam is measured by the array, and is directly proportional to torque in the bearings.

Abstract: The speed of the gas generator of a gas turbine engine is measured and summed with the rate of change of the gas generator speed and the sum is input to a schedule which outputs desired engine acceleration as a function of gas generator speed, the input thereby providing an anticipation to the schedule output so as to result in a dynamic shift of the schedule. In an exemplary embodiment of the invention in a helicopter fuel control, the amount of anticipation provided by the schedule input allows the fuel control to accurately control the engine to the desired acceleration schedule.

Abstract: A wedge-shaped block of pyrolytic graphite or other suitable anisotropic material cut along certain predetermined angular dimensions is used as a thermal expansion coefficient transformer to match the anisotropic thermal expansion coefficients of a lithium niobate or lithium tantalate IO chip to an isotropic substrate material such as 316 stainless steel or aluminum, or to match the isotropic thermal expansion coefficients of a silicon IO chip to an isotropic substrate material, the wedge being used as an intermediate block mounted between the IO chip and the substrate, the anisotropic material used as the thermal transformer having a thermal expansion coefficient which is greater than the value of the thermal expansion coefficient of the IO chip material in one direction, and having a thermal expansion coefficient which is lesser than the thermal expansion coefficient of the IO chip material in another direction.

Abstract: Control apparatus having two-fault tolerance for two position, motor operated actuators includes electronic circuitry for disconnection of the power return to the actuator motor armature thereby insuring that the motor will not be activated upon an inadvertent connection of power to either motor power input, and for indication of disconnection thereto. Testing determines the operatonal status of a motor relay and also determines inadvertent applications of power to the one of the pair of motor power inputs that is not connected to the power source through the position switch and one of the pair of limit switches. A relay and motor indication are operable to indicate either motor operation or inadvertent power interruptions in the one of the pair of motor power inputs most recently connected to the power source through the position switch and one of the pair of limit switches.