Electrical and Electronics
The scientific and technological development, behavior and application of electronic devices, circuits and systems involving the flow of electrons in semiconductors, gaseous media or a vacuum.
Magnetic Shield Using Proximity Coupled Spatially Varying Superconducting Order Parameters
The invention uses the superconducting "proximity effect" and/or the "inverse proximity effect" to form a spatially varying order parameter. When designed to expel magnetic flux from a region of space, the proximity effect(s) are used in concert to make the superconducting order parameter strongly superconducting in the center and more weakly superconducting toward the perimeter. The shield is then passively cooled through the superconducting transition temperature. The superconductivity first nucleates in the center of the shielding body and expels the field from that small central region by the Meissner effect. As the sample is further cooled the region of superconducting order grows, and as it grows it sweeps the magnetic flux lines outward.
Dynamic Range Enhancement of High-Speed Data Acquisition Systems
Electronic waveforms exist that exceed the capabilities of state-of-the-art data acquisition hardware that is commonly available. The electronic waveforms that need to be measured simultaneously contain wide bandwidth, high frequency content, a DC reference, high dynamic range, and a high crest factor. The NASA Glenn high-speed data acquisition system creates a voltage compression effect with a custom transfer function that is adapted to the voltage range, frequency bandwidth, and electrical impedance of both the test article and data acquisition device. The compression transfer function is later reversed (or decompressed) with a software algorithm to restore the original signal's voltage from the acquired data. The data is thus improved via better signal-to-noise ratio, better low-amplitude accuracy, better resolution, and preservation of high-frequency spectral content. The circuit can be realized with either passive components or both active and passive components. Either realization is specialized for the test article and data acquisition hardware. This is an early-stage technology requiring additional development. Glenn welcomes co-development opportunities.
Packaging for SiC Sensors and Electronics
Prior approaches to bonding a SiC sensor and a SiC cover member relied on either electrostatic bonding or direct bonding using glass frits. The problem with the former is that its relatively weak bond strength may lead to debonding during thermal cycling, while the latter requires the creation of apertures that can allow sealant to leak. Glenn's innovation uses NASA's microelectromechanical system direct chip attach (MEMS-DCA) technology that can be bulk-manufactured to reduce sensor costs. The MEMS-DCA process allows a direct connection to be made between chip and pins, thereby eliminating wire bonding. Sensors and electronics are attached in a single-stage process to a multifunctional package, which, unlike previous systems, can be directly inserted into the housing. Additional thick pins within the electrical outlet allow the package to be connected to external circuitry. Furthermore, because the top and bottom substrates' thermomechanical properties are similar to that of the sensors, the problem of mismatch in the coefficient of thermal expansion is significantly reduced, minimizing thermal cycling and component fatigue. By protecting sensors and electronics in temperatures up to 600°C, approximately twice what has previously been achievable, Glenn's innovation enables SiC components to realize one of their most exciting possibilities - direct placement within high-temperature environments.
Gated Chopper Integrator (GCI)
The gated chopper integrators function is to amplify low level signals without introducing excessive offset and noise and to do this with accurate and variable gain. The unique feature of the technology is the inherent demodulation present in the integrator which eliminates the need for filtering and allows the user to accurately vary the gain in finely graduated steps. The reduction of the offset of the amplifier is very efficient and lends itself to radiation hardened by design implementations. Since total dose can change the offset due to varying threshold voltages of CMOS transistors, the circuit adapts and compensates for any variations. The autozero integrator also adapts to its own varying offsets. The net outcome is variable, accurate gain that is very robust to supply variations, radiation effects and aging. The technology was developed as a multi-channel thermopile signal processor. Lab measurements indicate very accurate amplification with low offset and noise.
Microstrip Circuit and Material Characterization System
The Microstrip Circuit and Material Characterization System can measure superconducting film ohmic loss at millimeter wave frequencies using a vector network analyzer. The vector network analyzer measures amplitude and phase properties of the network parameters of the film. The system consists of a two-port waveguide structure. The ports are used to transmit and receive millimeter wave power into and out of the superconducting film. The waveguide structure is used to transform waveguide characteristic impedance to microstrip line impedance over broad ranges of frequencies to make contact with the superconducting film. The superconducting film contains microstrip line resonators that can be used to measure ohmic loss and the effective dielectric constant at various frequencies. The Microstrip Circuit and Material Characterization System functions by connecting to a millimeter wave transmitter and receiver. The system is used to measure transmission loss of a microstrip line sample. For superconducting microstrip film measurement, the device needs to be cooled below the superconductor's critical temperature in order to measure the film ohmic loss and the transmission line's propagation constant. The system can be used to measure loss in the microstrip line as low as 10 ppm. The system is operable within a temperature range from 0K to 320K.
Custom Application Specific Integrated Circuit for Detector Control and Data Acquisition
The ASIC receives signals from the detector via an analog-to digital converter (ADC). This ADC includes a full analog front-end with signal routing and pre-amplification. The digital signals are then routed through an Output Data Formatter and are directed to warm electronics. A digital Control component provides clocking for the detector and external serial control. The BIAS component provides quiet voltages to the detector. This electrical architecture minimizes thermal stress loads while maximizing signal integrity. The processing functions are performed at the highest allowable temperatures minimizing the number of components that require cooling.
Graphene-Based Reversible Nano-Switch/Sensor Schottky Diode Device
Glenn's graphene-based nanoSSSD provides dual-use functionality and reversibility characteristics in a compact and reliable package. The nanoSSSD can be connected to a visual and/or sound alarm that autonomously triggers in the presence of specially selected gases, such as ammonia, hydrogen, hydrocarbons, nitrogen oxides, or carbon monoxide. The device includes a doped substrate, an insulating layer disposed on the substrate, an electrode formed on the insulating layer, and one or more thin films of graphene deposited on an electrodized, doped silicon wafer. The graphene film acts as a conductive path between a gold electrode deposited on top of a silicon dioxide layer and the reversible side of the silicon wafer, so as to form a Schottky diode. The substrate in Glenn's innovative device can be fabricated with either n-doped or p-doped silicon, allowing the device to achieve enhanced compatibility with specific silicon-based nanoelectronic circuits as required. The graphene's two-dimensional nature maximizes the sensing area, and the device itself contains no moving parts, unlike other devices that offer dual switching/sensing functionality, which often make use of mechanical actuators such as cantilevers. Those devices are more complex to fabricate and more likely to reduce the mean-time-to-failure. By contrast, the relative simplicity of the Glenn nanoSSSD makes it more robust and therefore lends itself to settings where frequent replacement is not an option. This mechanism has the potential to revolutionize sensing/switching applications from embedded biomedical devices to jet turbine engines to homeland security screening systems.
Metallization for SiC Semiconductors
To avoid catastrophic failure, traditional electrical ohmic contacts must be placed at some distance from the optimal position (especially for sensors) in high-temperature environments. In addition, conventional metallization techniques incur significant production costs because they require multiple process steps of successive depositions, photolithography, and etchings to deposit the desired ohmic contact material. Glenn's novel production method both produces ohmic contacts that can withstand higher temperatures than ever before (up to 600°C), and permits universal and simultaneous ohmic contacts on n- and p-type surfaces. This makes fabrication much less time-consuming and expensive while also increasing yield. This innovative approach uses a single alloy conductor to form simultaneous ohmic contacts to n- and p-type 4H-SiC semiconductor. The single alloy conductor also forms an effective diffusion barrier against gold and oxygen at temperatures as high as 800°C. Glenn's extraordinary method enables a faster and less costly means of producing SiC-based sensors and other devices that provide quicker response times and more accurate readings for numerous applications, from jet engines to down-hole drilling, and from automotive engines to space exploration.
Microcontroller Altimeter (uCA)
The uCA combines a high accuracy integrated silicon pressure sensor with MOSFET technology to provide traditional Normally-Open and Normally-Closed switches capable of high power switching for a wide variety of applications. The output of the sensor and switches are provided to the user for real-time altitude determination as well as discrete altitude trip point knowledge. Updates to the altitude trip points are facilitated through USB programming, which allows for in-field adjustment and provides added flexibility late during integration and testing.
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