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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 343 records · Page 19

Benefits of Ka-band GaN MMIC High Power Amplifiers With Wide Bandwidth and High Spectral/Power Added Efficiencies for Cognitive Radio Platforms

A cognitive radio on a future NASA near-Earth spacecraft will be capable of sensing its environment and dynamically adapting its operating parameters to provide the desired SATCOM service to the mission. A key component that can enable this type of operation is a high-power amplifier (HPA) that resides on the radio platform. In this report, we present the RF performance characteristics of a Ka-band gallium nitride (GaN) monolithic microwave integrated circuit (MMIC) based HPA for cognitive radio platforms. These characteristics include the output power, gain, power added efficiency (PAE), RMS error vector magnitude (EVM), spectral efficiency, 3rdorder intermodulation distortion (IMD) products, spectrum, spectral regrowth, noise figure (NF), phase noise, and group delay. The data presented indicates that the HPA meets NTIA, military, and commercial spectral mask requirements. In addition, we discuss the benefits offered by the above performance characteristics toward the design and implementation of a cognitive radio platform. Furthermore, as examples, we discuss three potential use cases that apply artificial intelligence (AI) and machine learning (ML) techniques and exploit the performance characteristics discussed above to provide a knowledge-based cognitive radio platform design for SATCOM. Thus, cognitive radios with performance flexibility can enable roaming and provide seamless interoperability autonomously in the future between NASA, commercial, and other space networks owned by U.S. government agencies.

Gallium nitride↗

High-Cycle Fatigue Behavior of SiC-based Ceramic Matrix Composites (CMCs) at High Temperatures

High-cycle fatigue (HCF) behavior of a melt-infiltrated, pre-preg SiC/SiC ceramic matrix composite (CMC) was investigated using dogbone tensile specimens without and with simulated cooling holes at 1500 and 2400 °F. The CMC material used for this study was fabricated by GE Aviation and had a ply configuration of [0/90/0]3. HCF tests were conducted with an R-ratio of 0.6 and a cyclic frequency of 30 Hz. Runout in HCF was defined as 30 million cycles. Monotonic tensile tests were conducted at room temperature (RT) on as-received CMC specimens and on runout HCF specimens to determine residual tensile strengths. Digital image correlation (DIC) and acoustic emission (AE) techniques were used to monitor the initiation and progression of damage in RT tensile tests on specimens with and without holes. Microscopy was performed on the polished edge of specimens without cooling holes and on the polished face of specimens with cooling holes that were tested in HCF and achieved runout. Comparisons were made with baseline specimens. Fractography was performed to examine the fracture surfaces of samples that failed under different loading conditions.

Ceramic Matrix Composites↗

Efficient circuit triggers high-current, high-voltage pulses

Modified circuit uses diodes to effectively disconnect the charging resistors from the circuit during the discharge cycle. Result is an efficient parallel charging, high voltage pulse modulator with low voltage rating of components.

Green, E. D.↗

High efficiency, high frequency magnetic deflection driver

Electromagnetic deflection yoke stores energy during the scan and releases it in the flyback or retrace. The operation of the device involves a method of switching to a voltage high enough to dissipate the flyback pulse during the retrace time and then operating during the scan time at a much lower voltage.

Schaff, F. L.↗

High-energy, high-power, long-life battery

High-energy-density primary battery achieves energy densities of up to 130 watt hrs./lb. The electrochemical couple consists of a lithium anode, a copper-fluoride cathode, and uses methyl formate/lithium hexafluoroarsenate for the electrolyte. Once achieved, battery life is approximately 30 hours.

Abens, S. G.↗

Highly stable high-rate discriminator for nuclear counting

Pulse amplitude discriminator is specially designed for nuclear counting applications. At very high rates, the threshold is stable. The output-pulse width and the dead time change negligibly. The unit incorporates a provision for automatic dead-time correction.

English, J. J.↗