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Author Nagatsuma, T.; Hirata, A.; Royter, Y.; Shinagawa, M.; Furuta, T.; Ishibashi, T.; Ito, H.
Title (up) A 120-GHz integrated photonic transmitter Type Conference Article
Year 2000 Publication Proc. International topical meeting on microwave photonics (MWP 2000) Abbreviated Journal
Volume Issue Pages 225 - 228
Keywords THz, teraherts communications, terahertz communication channel, photodiode, transmitter
Abstract A photonics-based 120-GHz transmitter has been developed. A photodiode, a planar antenna and a silicon lens were integrated to form a compact millimeter-wave (MMW) emitter. The MMW signal emitted from the transmitter has been detected with a waveguide-mounted Schottky diode. The received power exceeded 100 μW, which is the highest value ever reported for photonic MMW transmitter at frequencies of >100 GHz
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Notes Approved no
Call Number Serial 595
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Author Khosropanah, P.; Merkel, H.; Yngvesson, S.; Adam, A.; Cherednichenko, S.; Kollberg, E.
Title (up) A distributed device model for phonon-cooled HEB mixers predicting IV characteristics, gain, noise and IF bandwidth Type Conference Article
Year 2000 Publication Proc. 11th Int. Symp. Space Terahertz Technol. Abbreviated Journal
Volume Issue Pages 474-488
Keywords HEB mixer numerical model, diffusion cooling channel, diffusion channel, distributed HEB model, distributed model
Abstract A distributed model for phonon-cooled superconductor hot electron bolometer (HEB) mixers is given, which is based on solving the one-dimensional heat balance equation for the electron temperature profile along the superconductor strip. In this model it is assumed that the LO power is absorbed uniformly along the bridge but the DC power absorption depends on the local resistivity and is thus not uniform. The electron temperature dependence of the resistivity is assumed to be continuous and has a Fermi form. These assumptions are used in setting up the non-linear heat balance equation, which is solved numerically for the electron temperature profile along the bolometer strip. Based on this profile the resistance of the device and the IV curves are calculated. The IV curves are in excellent agreement with measurement results. Using a small signal model the conversion gain of the mixer is obtained. The expressions for Johnson noise and thermal fluctuation noise are derived. The calculated results are in close agreement with measurements, provided that one of the parameters used is adjusted.
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Publisher Place of Publication University of Michigan, Ann Arbor, MI USA Editor
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Notes Approved no
Call Number Serial 893
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Author Floet D. W.; Gao J. R.; Klapwijk T. M.; de Korte P. A. J.
Title (up) Bias Dependence of the Thermal Time Constant in Nb Superconducting Diffusion-Cooled HEB Mixers Type Journal Article
Year 2000 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.
Volume 77 Issue Pages 1719
Keywords
Abstract We present an experimental study of the intermediate frequency bandwidth of a Nb diffusion-cooled hot-electron bolometer mixer for different bias voltages. The measurements show that the bandwidth increases with increasing voltage. Analysis of the data reveals that this effect is mainly caused by a decrease of the intrinsic thermal time of the mixer and that the effect of electrothermal feedback through the intermediate frequency circuit is small. The results are understood using a qualitative model, which takes into account the different effective diffusion constants in the normal and superconducting domains.
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Notes Approved no
Call Number RPLAB @ atomics90 @ Serial 971
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Author Semenov, A. D.; Hübers, H.-W.; Schubert, J.; Gol'tsman, G. N.; Elantiev, A. I.; Voronov, B. M.; Gershenzon, E. M.
Title (up) Design and performance of the lattice-cooled hot-electron terahertz mixer Type Journal Article
Year 2000 Publication J. Appl. Phys. Abbreviated Journal J. Appl. Phys.
Volume 88 Issue 11 Pages 6758-6767
Keywords HEB mixer, charge imbalance, HF current distribution
Abstract We present the measurements and the theoreticalmodel of the frequency-dependent noise temperature of a superconductor lattice-cooled hot-electron bolometer mixer in the terahertz frequency range. The increase of the noise temperature with frequency is a cumulative effect of the nonuniform distribution of the high-frequency current in the bolometer and the charge imbalance, which occurs at the edges of the normal domain and at the contacts with normal metal. We show that under optimal operation the fluctuation sensitivity of the mixer is determined by thermodynamic fluctuations of the noise power, whereas at small biases there appears additional noise, which is probably due to the flux flow. We propose the prescription of how to minimize the influence of the current distribution on the mixer performance.
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ISSN 0021-8979 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 306
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Author Wright, E. L.; Reese, E. D.
Title (up) Detection of the cosmic infrared background at 2.2 and 3.5 microns using DIRBE observations Type Journal Article
Year 2000 Publication Astrophys. J. Abbreviated Journal
Volume 545 Issue 1 Pages 43-55
Keywords IR applications
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ISSN 0004-637X ISBN Medium
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Notes Approved no
Call Number Serial 486
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