Novel transmission lines for the submillimeter-wave region
Article Abstract:
The narrow-beam, high-resolution antennas required by such applications as intelligent computer control guidance, command systems for space applications, and sensors operating in an optically opaque environment work in the submillimeter-wave range. Low-loss transmission lines are designed in two different ways: by extending the millimeter-wave monolithic technology to higher frequencies, which uses planar conductors for the guidance of waves; and by extending optical techniques to lower frequencies, which results in low-loss, quasi-planar lines made exclusively of intrinsic semiconducting materials. The first approach can be used to develop low-loss planar and nonplanar lines, but it is limited to the lower end of the submillimeter-wave spectrum. The four types of novel monolithic waveguides that may be used in the submillimeter frequency range are monolithic dielectric guides, microshield lines, lens-supported coplanar lines, and silicon micromachined waveguides.
Publication Name: Proceedings of the IEEE
Subject: Electronics
ISSN: 0018-9219
Year: 1992
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Optically pumped submillimeter laser heterodyne receivers: astrophysical observations and recent technical developments
Article Abstract:
The submillimeter spectral region's importance is shown by NASA's plans for a series of submillimeter space missions, including the Small Explorer Submillimeter Wave Astronomy Satellite and an intermediate class Explorer mission. NASA also plans to upgrade its existing Kuiper Airborne Observatory with the Stratospheric Observatory for Infrared Astronomy. The technical challenges posed by these submillimeter missions were discussed at the Workshop Proceedings for Sensor Systems for Space Astrophysics in the 21st Century. The technical requirements for submillimeter heterodyne receivers, as seen by workshop participants, are reviewed. The four categories into which the technology shortcomings for terahertz receivers fall are local oscillators, mixers, focal-plane arrays, and spectrometers. The review focuses on the use of optically pumped submillimeter lasers as a local oscillator source.
Publication Name: Proceedings of the IEEE
Subject: Electronics
ISSN: 0018-9219
Year: 1992
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Submillimeter-wavelength heterodyne spectroscopy and remote sensing of the upper atmosphere
Article Abstract:
The earth's upper troposphere, stratosphere, mesosphere, and lower thermosphere can be studied on a global scale using submillimeter- and millimeter-wavelength heterodyne spectroscopy. A technique is described that measures atmospheric thermal emission spectra as the instrument field of view is scanned through the limb from above. The measured emission spectra can be used to determine atmospheric profiles of molecular abundances, temperature, pressure, wind, and magnetic field. The highest altitudes that can be measured are limited by low signal strengths. The lower altitudes that can be measured are limited by tropospheric attenuation by water and low signal strengths for other molecules. Ice clouds and other particles have little effect on the signals, which allows measurements in regions where heterogeneous chemistry can occur.
Publication Name: Proceedings of the IEEE
Subject: Electronics
ISSN: 0018-9219
Year: 1992
User Contributions:
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