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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Double-loop frequency selective surfaces for multi frequency division multiplexing in a dual reflector antenna

A multireflector antenna utilizes a frequency-selective surface (FSS) in a subreflector to allow signals in two different RF bands to be selectively reflected back into a main reflector and to allow signals in other RF bands to be transmitted through it to the main reflector for primary focus transmission. A first approach requires only one FSS at the subreflector which may be an array of double-square-loop conductive elements. A second approach uses two FSS's at the subreflector which may be an array of either double-square-loop (DSL) or double-ring (DR). In the case of DR elements, they may be advantageously arranged in a triangular array instead of the rectangular array for the DSL elements.

Wu, Te-Kao↗
NASA NTRS2001

Fixed-frequency and Frequency-agile (au, HTS) Microstrip Bandstop Filters for L-band Applications

In this work, we report on the performance of a highly selective, compact 1.83 x 2.08 cm(exp 2) (approx. 0.72 x 0.82 in(exp 2) microstrip line bandstop filter of YBa2CU3O(7-delta) (YBCO) on LaAlO3 (LAO) substrate. The filter is designed for a center frequency of 1.623 GHz for a bandwidth at 3 dB from reference baseline of less than 5.15 MHz, and a bandstop rejection of 30 dB or better. The design and optimization of the filter was performed using Zeland's IE3D circuit simulator. The optimized design was used to fabricate gold (Au) and High-Temperature Superconductor (HTS) versions of the filter. We have also studied an electronically tunable version of the same filter. Tunability of the bandstop characteristics is achieved by the integration of a thin film conductor (Au or HTS) and the nonlinear dielectric ferroelectric SrTiO3 in a conductor/ferroelectric/dielectric modified microstrip configuration. The performance of these filters and comparison with the simulated data will be presented.

Saenz, Eileen M.↗
NASA NTRS2006

A 260-340 GHz Dual Chip Frequency Tripler for THz Frequency Multiplier Chains

We designed and fabricated a fix-tuned balanced frequency tripler working in the 260-340 GHz band to be the first stage of a x3x3x3 multiplier chain to 2.7 THz. The design of a dual-chip version of this multiplier featuring an input splitter / output combiner as part of the input / output matching networks of both chips - with no degradation of the expected bandwidth and efficiency- will be presented.

Schottky diodes↗
DOE OSTI2020

Frequency modulated radio frequency electric field for ion manipulation

A method of manipulating ions comprises injecting ions between a first surface and a second surface positioned parallel to and spaced apart from each other and defining a central axis therebetween, wherein the first surface comprises first outer electrodes coupled to the first surface and a first inner array of electrodes coupled to the first surface and positioned between the first outer electrodes, wherein the second surface comprises second outer electrodes coupled to the second surface and a second inner array of electrodes coupled to the second surface and positioned between the second outer electrodes, and applying a frequency modulated RF voltage to at least one electrode of the first inner array of electrodes or the second inner array of electrodes to confine ions between the first surface and the second surface and to guide ions between the first surface and the second surface along the central axis.

42 ENGINEERING↗
DOE OSTI2016

High‐frequency daily temperature variability in China and its relationship to large‐scale circulation

ABSTRACT Two measures of intra‐seasonal variability, indicated respectively by standard deviations ( SD ) and day‐to‐day ( DTD ) fluctuations denoted by absolute differences between adjacent 2‐day periods, as well as their relationships with large‐scale circulation patterns were investigated in China during 1962–2008 on the basis of homogenized daily temperature records from 549 local stations and reanalysis data. Our results show that both the SD and DTD of daily minimum temperatures ( T min ) in summer as well as the minimum and maximum temperatures in winter have been decreasing, while the daily maximum temperature ( T max ) variability in summer is fluctuating more, especially over southern China. In summer, an attribution analysis indicates that the intensity of the Western Pacific Subtropical High ( WPSH ) and high‐level East Asian Subtropical Jet stream ( EASJ ) are positively correlated with both SD and DTD , but the correlation coefficients are generally greater with the SD than with the DTD of the daily maximum temperature, T max . In contrast, the location of the EASJ shows the opposite correlation pattern, with intensity regarding the correlation with both SD and DTD . In winter, the Arctic Oscillation ( AO ) is negatively correlated with both the SD and DTD of the daily minimum temperature, but its intra‐seasonal variability exhibits good agreement with the SD of the T min . The Siberian High acts differently with respect to the SD and DTD of the T min , demonstrating a regionally consistent positive correlation with the SD . Overall, the large‐scale circulation can well explain the intra‐seasonal SD, but DTD fluctuations may be more local and impacted by local conditions, such as changes in the temperature itself, the land surface, and so on.

Wu, Fu‐Ting↗