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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 1,495 records · Page 83
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

W-Band On-Wafer Measurement of Uniplanar Slot-Type Antennas

Uniplanar slot-type antennas such as coplanar waveguide fed single- and dual-polarized slot-ring antennas and double folded-slot antennas are characterized using a millimeter-wave network analyzer and on-wafer measurement techniques. The antennas are designed to be mounted on a dielectric lens to minimize power loss into substrate modes and realize high-gain antenna patterns. On-wafer measurements are performed by placing the antenna wafer on a thick dielectric spacer of similar e(sub t) and eliminating the reflection from the probe station chuck with time-domain gating. The measured results agree well with method-of-moments simulations.

Raman, Sanjay↗
NASA NTRS2006

Ka-Band Wide-Bandgap Solid-State Power Amplifier: Prototype Combiner Spurious Mode Suppression and Power Constraints

Results of prototype hardware activities related to a 120-W, 32-GHz (Ka-band) solid-state power amplifier (SSPA) architecture study are presented. Spurious mode suppression and the power-handling capability of a prototype 24-way radial combiner and a prototype 2-way septum binary combiner were investigated. Experimental data indicate that a commercial absorptive filter, designed to pass the circular TE01 mode, effectively suppressed the higher-order modes generated by a narrowband, flower-petal-type mode transducer. However, the same filter was not effective in suppressing higher-order modes generated by the broadband Marie mode transducer that is used in the prototype waveguide radial combiner. Should greater filtering be required by a particular SSPA application, a broadband mode filter that can suppress specifically those higher-order modes that are generated by the Marie transducer will need to be developed. A back-to-back configuration of the prototype radial combiner was tested with drive power up to approximately 50 W. No anomalous behavior was observed. Power measurements of the septum combiner indicate that up to 10-W radio frequency (RF) can be dissipated in the integrated resistive element before a permanent performance shift is observed. Thus, a given adder (a single-stage, 2-way combiner) can safely combine two 20-W sources, and the adder will not be damaged in the event of a source failure. This result is used to calculate the maximum source power that can be safely combined as a function of the number of sources combined and the number of source failures allowed in a multi-stage combiner. The analysis shows that SSPA power >140 W can be generated by power combining 16 sources producing 10 W each. In this configuration, up to three sources could fail with the guarantee that the combiner would not be damaged. Finally, a modified prototype septum combiner design was verified. The improved design reduced the assembly time from over 2 hours to about 15 minutes per adder.

Khan, P.↗
NASA NTRS2002

THz frequency multiplier chains base on planar Schottky diodes

The Herschel Space Observatory (HSO), an ESA cornerstone mission with NASA contribution, will enable a comprehensive study of the galactic as well as the extra galactic universe. At the heart of this exploration are ultra sensitive coherent detectors that can allow for high-resolution spectroscopy. Successful operation of these receivers is predicated on providing a sufficiently powerful local oscillator (LO) source. Historically, a versatile space qualified LO source for frequencies beyond 500 GHz has been difficult if not impossible. This paper will focus on the effort under way to develop, build, characterize and qualify a LO chain to 1200 GHz (Band 5 on HSO) that is based on planar GaAs diodes mounted in waveguide circuits. State-of-the-art performance has been obtained from a three-stage ( x2 x 2 x 3 ) multiplier chain that can provide a peak output power of 120 uW (1178 GHz) at room temperature and a peak output power of 190 uW at 1183 GHz when cooled to 113 K. Implementation of this LO source for the Heterodyne Instrument for Far Infrared (HIFI) on HSO will be discussed in detail.

oscillator spectroscopy↗
NASA NTRS2002

Improved equivalent circuit for twin slot terahertz receivers

Series-fed coplanar waveguide embedding circuits are being developed for terahertz mixers using, in particular, submicron-sized superconducting devices, such as hot electron bolometers as the nonlinear element. Although these mixers show promising performance, they usually also show a considerable downward shift in the center frequency, when compared with simulations obtained by using simplified models. This makes it very difficult to design low-noise mixers for a given THz frequency. This shiftis principally caused by parasitics due to the extremely small details (in terms of wavelength) of the device, and by the electrical properties of the RF choke filter in the DC/IF line. In this paper, we present an improved equivalent network model of such mixer circuits which agrees with measured results at THz frequencies and we propose a new set of THz bolometric mixers that have been fabricated and are currently being tested.

HEB slot antennas CPW↗
NASA NTRS1997

Designing Dielectric Grating Filters with PGAPACK

The chapter is concerned with the design of planar dielectric layer diffraction gratings, which exhibit sharp resonances due to the coupling of exterior evanescent diffractive fields to the leaky modes of dielectric waveguides.

genetic algorithms↗
NASA NTRS1997

Experimental Verification of the Pulse Shepherding Concept in Dispersion-Shifted Single-Mode Fiber for Bit-Parallel Wavelength Links

A new way to dynamically control in-flight pulses by a co-propagating shepherd pulse in a wavelength divsion multiplexed (WDM) single-mode fiber system was proposed at the MPPOI '96 Conference. That system functionally resembles an optical fiber ribbon cable, except that all the bits pass on one fiber optic waveguide.

Pulse Shepherding Bit-Parallel Wavelength Links↗
NASA NTRS1995

High Power Photodetectors for Space Communications Applications

High power photodetectors in coplanar waveguide and distributed traveling-wave structures have been under development for communications applications. The distributed photodetectors demonstrated 70percent efficiency with a linear response up to 25 mW of optical power input.

High Power Photodetectors↗
NASA NTRS1995

High Power Amplifier Harmonic Output Level Measurement

A method is presented for the measurement of the harmonic output power of high power klystron amplifiers, involving coherent hemispherical radiation pattern measurements of the radiated klystron output. Results are discussed for the operation in saturated and unsaturated conditions, and with a waveguide harmonic filter included.

klystron amplifiers harmonic output power measurem↗
NASA NTRS1993

DSS-13 S-Band Design Optimization Using The Focal-Plane Method

In this paper, the Focal-Plane (Complex-Conjugate Phase-Matching) Method is used to select the appropriate gain and location of a feed for S-Band (2.295 GHz) operation of DSS-13, the new NSA/JPL Deep Space Network (DSN) 34-m Beam WaveGuide (BWG) antenna. It is found empirically that the Focal-Plane Method gives a better design in terms of the G/T figure than previous S-Band designs.

Focal Plane S-Band↗
NASA NTRS1994

X/Ka-Band Dual Frequency Horn Design

The Deep Space Network has a need for a dual frequency horn for simulation dual frequency operation in a beam waveguide antenna. The dual frequency horn will receive X-band (8.4-8.5 GHz), KABLE frequency (33.6-33.8 GHz), and DSN Ka-band downlink (31.8-32.3 GHz) signals simultaneously.

X-Band Ka-Band↗
NASA NTRS2003

Room-temperature continuous operation of InAsSb quantum-dot lasers near 2 mu m based on (100) InP substrate

Single-stack InAsSb self-assembled quantum-dot lasers based on (001) InP substrate have been grown by metalorganic vapor-phase epitaxy. The narrow ridge waveguide lasers lased at wavelengths near 2 mu m up to 25 degrees C in continuous-wave operation. At room temperature, a differential quantum efficiency of 13 percent is obtained and the maximum output optical power reaches 3 mW per facet with a threshold current density of 730 A/cm(sup 2). With increasing temperature the emission wavelength is extremely temperature stable, and a very low wavelength temperature sensitivity of 0.05 nm/degrees C is measured, which is even lower than that caused by the refractive index change.

Semiconductor lasers quantum dots↗