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Results for “submillimeter wavelengths”

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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

BIN Diode For Submillimeter Wavelengths

Diode formed by selective doping during epitaxial growth, starting with semi-insulating substrate. Use of high-mobility semiconductors like GaAs extends cutoff frequency. Either molecular-beam epitaxy (MBE) or organometallic chemical-vapor deposition used to form layers of diode. Planar growth process permits subsequent fabrication of arrays of diodes by standard photolithographic techniques, to achieve quasi-optical coupling of submillimeter radiation. Useful for generation of harmonics or heterodyne mixing in receivers for atmospheric and space spectroscopy operating at millimeter and submillimeter wavelengths. Used as frequency doublers or triplers, diodes of new type extend frequency range of present solid-state oscillators.

Maserjian, J.↗
NASA NTRS1992

Varactor diodes for millimeter and submillimeter wavelengths

Whisker-contacted GaAs Schottky barrier varactor diodes are the most common high-frequency multiplier element in use today. They are inherently simple devices that have very high frequency response and have been used to supply local oscillator power for Schottky heterodyne receivers to frequencies approaching 700 GHz. This paper discusses the development of improved varactor diode technology for space based applications at millimeter and submillimeter wavelengths.

Rizzi, Brian J.↗
NASA NTRS2013

Ultra-Compact, Superconducting Spectrometer-on-a-Chip at Submillimeter Wavelengths

Small size, wide spectral bandwidth, and highly multiplexed detector readout are required to develop powerful multi-beam spectrometers for high-redshift observations. Currently available spectrometers at these frequencies are large and bulky. The grating sizes for these spectrometers are prohibitive. This fundamental size issue is a key limitation for space-based spectrometers for astrophysics applications. A novel, moderate-resolving-power (R-700), ultra-compact spectrograph-on-a-chip for millimeter and submillimeter wavelengths is the solution.

Chattopadhyay, Goutam↗
NASA NTRS1974

Reflection beam isolator for submillimeter wavelengths

Magnetoplasma reflection beam isolators for submillimeter wave use are discussed. The basic configuration used is that of the Kerr transverse magneto-optical effect. Theoretical and experimental data at 337 microns using InSb as a plasma are given.

Kanda, M.↗
NASA NTRS1977

An optically pumped submillimeter wavelength regenerative amplifier

An optically pumped regenerative submillimeter laser amplifier is described. The amplifier uses a waveguide cavity resonator, and a Fabry-Perot interferometer composed of two dielectric-coated mirrors serves as input and output port for the submillimeter signal. Use of two mirrors enabled obtaining variations of up to 6:1 in transmission by varying the mirror spacing. When the 373-micron transition in CH3CN is excited in the oscillator by the CO2 laser pump beam, the received signal with amplification is about nine times the unamplified signal.

Galantowicz, T. A.↗
NASA NTRS1978

Composite bolometers for submillimeter wavelengths

The fabrication and optimization of composite submillimeter wave bolometers with metal film absorbing elements and doped Ge thermometers are described. Performance characteristics are given for 4 x 4-mm bolometers designed for operation at both He-4 and He-3 temperatures. The performance expected from such bolometers when they are optimized for various values of background loading is calculated. Current dependent noise, which can arise from any of several sources, is included in the analysis. This can make it impossible to reach the background fluctuation noise limit. Feed structures for these bolometers which employ Winston light concentrators are described.

Nishioka, N. S.↗
NASA NTRS1996

Investigation of Passive Atmospheric Sounding Using Millimeter- and Submillimeter- Wavelength Channels

This report summarizes progress made during the period from July 1, 1994 through June 30, 1996 on the development of satellite-based observational techniques for high resolution imaging of precipitation and sounding of atmospheric ice and water vapor using passive microwave radiometers in the millimeter (MMW)- and submillimeter (SMMW)-wavelength. This is being achieved by radiative transfer modeling a millimeter and submillimeter wave frequencies and by the development and operation of an airborne millimeter wave imaging radiometer (MIR). The MIR has been used in both airborne and ground-based experiments. Its primary application is to provide calibrated radiometric imagery to verify MMW and SMMW radiative transfer models in clear air, cloud, and precipitation and to develop retrieval techniques using MMW and SMMW channels. The MIR imagery over convective storm cells has been used to illustrate the potentially useful cloud and water vapor sensing and storm-cell mapping capabilities of SMMW channels. The radiometric data has also been used to analyze radiative transfer model discrepancies caused by water vapor errors in radiosondes. The MMW and SMMW channels can be used to extend the altitude that water vapor sounding can be performed up into the lower stratosphere. Together, the use of both SMMW and MMW channels are expected to provide additional observational degrees of freedom related to cloud ice particle size.

Gasiewski, Albin J.↗
NASA NTRS1995

Josephson frequency meter for millimeter and submillimeter wavelengths

Frequency measurements of electromagnetic oscillations of millimeter and submillimeter wavebands with frequency growth due to a number of reasons become more and more difficult. First, these frequencies are considered to be cutoffs for semiconductor converting devices and one has to use optical measurement methods instead of traditional ones with frequency transfer. Second, resonance measurement methods are characterized by using relatively narrow bands and optical ones are limited in frequency and time resolution due to the limited range and velocity of movement of their mechanical elements as well as the efficiency of these optical techniques decrease with the increase of wavelength due to diffraction losses. That requires a priori information on the radiation frequency band of the source involved. Method of measuring frequency of harmonic microwave signals in millimeter and submillimeter wavebands based on the ac Josephson effect in superconducting contacts is devoid of all the above drawbacks. This approach offers a number of major advantages over the more traditional measurement methods, that is one based on frequency conversion, resonance and interferometric techniques. It can be characterized by high potential accuracy, wide range of frequencies measured, prompt measurement and the opportunity to obtain a panoramic display of the results as well as full automation of the measuring process.

Anischenko, S. E.↗
NASA NTRS2005

Heterodyne arrays at submillimeter wavelengths

Heterodyne receivers, which down-convert radio frequency (RF) signals to intermediate frequency (IF) signals - preserving the amplitude and phase information of the incoming radiation, are generally the detector of choice for high resolution spectroscopic studies in astrophysics and planetary remote sensing.

submillimeter wavelength↗
NASA NTRS2005

Future of heterodyne receivers at submillimeter wavelengths

In this review paper we examine these issues very carefully and describe the novel receivers being designed to make heterodyne instruments more competitive. It will be shown that heterodyne instruments will still have significant roles to play in the near future.

heterodyne↗
NASA NTRS1992

SALSA - A lunar submillimeter-wavelength array

A conceptual design for a Synthesis Array for Lunar Submillimeter Astronomy (SALSA) is described with emphasis on information relevant to its implementation. SALSA is optimized to synthesize images of astronomical sources at wavelengths between 60 and 300 microns with an angular resolution of 10 milliarcseconds at the shortest wavelength. The discussion covers engineering considerations and descriptions of subsystems, including the environmental shield, antenna, and beam transport.

Mahoney, M. J.↗
NASA NTRS1989

Study of optical output couplers for submillimeter wavelength backward-wave oscillators (BWO's)

Several scaled experiments of optical output couplers for submillimeter backward-wave oscillators (BWOs). Various designs of planar antennas (Vivaldi horns) lens-feed systems (hyperhemispherical lens) were constructed and tested between 20 and 100 GHz using a spectrum analyzer. The lens system was also tested at 337 GHz using a CO2 pumped FIR laser. It is found that Vivaldi horns have unsatisfactory resonances, perhaps because the horns studied were relatively short. Several techniques to maximize and flatten the frequency response of these horns are presented. The results suggest that alternate coupling schemes are superior to Vivaldi horns.

Cook, Jerry D.↗
NASA NTRS1991

Far-infrared and submillimeter-wavelength observations of star-forming dense cores. I - Spectra

Far-infrared and submillimeter photometry of 10 low-mass star formation regions containing embedded IRAS sources is presented. These new observations define the peak of the spectral energy distributions of these objects and provide more precise estimates of their bolometric luminosities. Two new sources, L1527 and L483, are among the reddest known low-mass objects, with spectral energy distribution peaks at 100-200 microns and extremely steep IRAS slopes. These cold sources have spectra which are similar to blackbodies of 30-40 K but have significant excess emission on the Wien side. Models of the spectral energy distributions using a spherically symmetric core structure indicate that these sources have visual extinctions greater than 1000 mag. However, models with these large extinctions predict too little near-infrared emission. A nonspherically symmetric distribution of circumstellar material may play a role in the generation of the extra near-infrared emission.

Ladd, E. F.↗
NASA NTRS1977

A directional filter diplexer using optical techniques for millimeter to submillimeter wavelengths

An optical diplexer for injection of a local oscillator into a mixer, useful in the submillimeter and short millimeter range, is described. It has very low insertion loss for both the signal and local oscillator (LO) and high rejection of LO noise. The measured performance of a unit tested at 337 GHz indicates a loss of about 0.2 dB for both inputs and 20-dB noise rejection.

Erickson, N. R.↗
NASA NTRS1971

The use of semiconductors in nonreciprocal devices for submillimeter wavelengths.

This paper reviews the use of anisotropic effects in a passive semiconductor magnetoplasma for the development of submillimeter isolators and circulators. The emphasis is on two schemes that are applicable over the far infrared portion of the spectrum. The theory of transmission devices depending on Faraday rotation is described, and experiments are discussed. At far infrared wavelengths it is not necessary to cool the semiconductor in order to achieve low forward loss. Some experimental results are available in this frequency range, and a theoretical evaluation of device performance is given. Reflection devices in which the desired signal does not propagate through the semiconductor, but is reflected off of its surface, are also discussed. Experimental results show that these devices can have a low forward loss; a variety of novel geometrical arrangements are able to improve isolator performance. Theoretical results indicating satisfactory performance for a far infrared isolator using InSb at room temperature are presented.

Hayes, R. E.↗