Electrical and Electronics
NASA's portfolio of electrical and electronics technologies represents a vast array of innovative solutions for a wide range of applications. Whether you are looking for solutions to power a spacecraft, improve the efficiency of an electric vehicle, or enhance the performance of a consumer product, NASA's portfolio of electrical and electronics technologies has something to offer.
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.
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.
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.
Polymer Nanofiber-Based Reversible Nano-Switch/Sensor Schottky Diode Device
Glenn's innovative nanoSSSD device includes a doped semiconducting substrate, an insulating layer deposited on the substrate, an electrode formed on the insulating layer, and at least one polymer nanofiber deposited on the electrode. The deposited nanofiber provides an electrical connection between the electrode and the substrate, serving as the electro-active element in the device. The nanofiber is generally composed of a customized polymer (e.g., polyaniline) that is extremely sensitive to the adsorption and desorption of a single gas molecule. As gas molecules are adsorbed and desorbed, the resistivity of the customized polymer also changes, providing its sensing capacity. When the nanoSSSD device senses a selected gaseous species, the switching portion of the device automatically actuates, sending a signal to the control component. This control component activates the output (warning) device. In addition to its ability to detect harmful gases (including ammonia, hydrogen, hydrocarbons, nitrogen oxides, carbon monoxide, and carbon dioxide), Glenn's device can also feature conducting polymers that are sensitive to UV radiation. Glenn's nanoSSSD technology has great commercial potential, particularly in situations where frequent replacement of the switch/sensor is impractical.
Using the Power Grid for Geophysical Imaging
This technology utilizes the U.S. high-voltage power transmission grid system as an extremely large antenna to extract unprecedented spatiotemporal space physical and geological information from distributed GIC observations. GICs are measured using differential a magnetometer technique involving one fluxgate magnetometer under the transmission line and another reference magnetometer station nearby. The reference station allows subtraction of the natural field from the line measurement, leaving only the GIC-related Biot-Savart field. This allows inversion of the GIC amplitude. The magnetometer stations are designed to operate autonomously. They are low-cost, enabling large scale application with a large number of measurement locations.
Nanostructure-Based Vacuum Channel Transistor
A planar lateral air transistor was fabricated using standard silicon semiconductor processing. The emitter and collector were sub-lithographically separated by photoresist ashing, with the curvature of the tip controlled by the thermal reflow of the photoresist. The gap can be shrunk as small as 10nm using this process. Since the nanogap separating the emitter and collector is smaller than the electron mean free path in air, vacuum is not needed. The present structure exhibits superior gate controllability and negligible gate leakage current due to adoption of the gate insulator. The device has potential for high performance and low power applications; also, since vacuum as the carrier transport medium is immune to high temperature and radiation, the proposed nanotransistors are ideal for extreme environments. Process and layout refinements such as coating a low work function material on the emitter, reducing the overlap area and optimizing the oxide thickness can potentially improve the cut-off frequency well into the THz regime.
Analog Signal Correlating
Each of two analog signals (channels A and B) is converted to a digital bit stream by phase correcting it and comparing it to an average of itself at a sampling clock rate f. The hard-limited conversions of A and B are bitwise compared to measure the level of similarity between the two by the OBDC. This similarity measurement X is equal to the maximum possible Hamming distance (N bits in disagreement) minus the measured number of bits in disagreement. The OBDC functions are embedded into a field programmable gate array (FPGA). The OBDC is made up of two shift registers containing the current sample values (of length N) from each of the two input channels (A and B). During each sample clock, a new sample from each A and B input is clocked into the input linear shift register for each respective channel; this input shifts the current values in the linear shift register. Once the inputs have been clocked in, the correlation routine can start. Once the correlation value has been calculated, this result is forwarded to compare with the max correlation value register. If the X value is greater than the current max correlation value, then the max correlation value becomes X, and the shift counter register is latched and put into the best correlation index register, providing the index of the current best correlation. This index is the number of sample clock periods difference between the two input signals and thus, for sample clock rate f, indicates the delay between the signals A and B. This is an early-stage technology requiring additional development. Glenn welcomes co-development opportunities.
Chip with micro-hotplate for self-healing and sustainable electronics
Heat treatment, also known as annealing, is a common step in the semiconductor fabrication process. A build-up of radiation-induced localized charge within the semiconductor and insulator alters local field distribution, threshold voltage and leakage current. NASA's patent-pending technology implements an annealing process on a system level directly on a chip for annealing defects and improving device performance with heating done in the laboratory. The annealing may be performed inside an oven, or upon a hotplate. A system on microheater provides defect annealing capability for recovering bulk trapped charges and interface states. The healing starts simply by heating the chip in a process that can be compared to that of humans immune system - something capable of detecting and quickly responding to any number of possible assaults in order to keep the larger system working optimally. A microheater is monolithically integrated on the backside of a generic Complementary Metal Oxide Semiconductor (CMOS) chip for an on-chip annealing system (left Figure 1(b)). Compared to a stacked microheater, the monolithic integration reduces the die profile, which accordingly enhances the heating power efficiency and heating/cooling rates, which was verified experimentally and numerically. The self-healing microheater is controlled by a temperature feedback circuit to maintain the desired temperature. All circuits under the treatment are unbiased in order to avoid any side effects on normal devices. A control circuit block is programmed to monitor a device parameter shift such as the threshold voltage on the same chip in order to determine the need for treatment. A control circuit triggers the micro hotplate and senses the temperature to adjust the target temperature and duration. The microheater and the system-on-chip are fabricated separately and stacked into a single package, which can be implemented on any arbitrary commercial-off-the-shelf device as a generic approach.
In Situ Wire Damage Detection and Rerouting System
The tester was designed to monitor electrical faults in either online or offline modes of operation. In the online mode, wires are monitored without disturbing their normal operation. A cable can be monitored several times per second in the offline mode, and once per second in the online mode. The online cable fault locator not only detects the occurrence of a fault, but also determines the type of fault (short/open/intermittent) and the location of the fault. This enables the detection of intermittent faults that can be repaired before they become serious problems. Since intermittent faults occur mainly during operations, a built-in memory device stores all relevant fault data. This data can be displayed in real time or retrieved later so maintenance and repairs can be completed without spending countless hours attempting to pinpoint the source of the problem. Hardware and algorithms have also been developed to safely, efficiently, and autonomously transfer electrical power and data connectivity from an identified damaged/defective wire in a cable to an alternate wire path. This portion of the system consists of master and slave units that provide the diagnostic and rerouting capabilities. A test pulse generated by the master unit is sent down an active wire being monitored by the slave unit. When the slave unit detects the test pulse, it routes the pulse back to the master unit through a communication wire. When the master unit determines that a test pulse is not being returned, it designates that wire as faulty and reroutes the circuit to a spare wire.
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