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| Author |
Kasparek, W; Fernandez, A.; Hollmann, F; Wacker, R. |
| Title |
Measurements of ohmic losses of metallic reflectors at 140 GHz using a 3-mirror resonator technique |
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Journal Article |
| Year |
2001 |
Publication |
Int. J. Infrared and Millimeter Waves |
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| Volume |
22 |
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11 |
Pages |
1695-1707 |
| Keywords |
mirror, reflection index, emissivity, Fabry-Perot interferometer, subterahertz, subTHz |
| Abstract |
The reflectivity of metallic mirrors in the millimeter wave region does not only depend on the material, but also on the structure and roughness of the surface. We have performed measurements of the reflectivity of various plane and grooved metallic and graphite samples at 140 GHz. The technique is based on the comparison of the quality factor of a 2-mirror reference resonator with the quality factor of a 3-mirror resonator which has identical dimensions and includes the mirror to be tested. After a brief presentation of the theory, the set-up is described and the reflection loss for various aluminium and copper mirrors as well as vacuum compatible materials for applications in thermonuclear fusion experiments are presented and discussed. |
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581 |
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| Author |
Maezawa, Hiroyuki |
| Title |
Application of superconducting hot-electron bolometer mixers for terahertz-band astronomy |
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Journal Article |
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2015 |
Publication |
IEICE Trans. Electronics |
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98 |
Issue |
3 |
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196-206 |
| Keywords |
HEB mixer applications, HEB applications |
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Recently, a next-generation heterodyne mixer detector – a hot electron bolometer (HEB) mixer employing a superconducting microbridge – has gradually opened up terahertz-band astronomy. The surrounding state-of-the-art technologies including fabrication processes, 4 K cryostats, cryogenic low-noise amplifiers, local oscillator sources, micromachining techniques, and spectrometers, as well as the HEB mixers, have played a valuable role in the development of super-low-noise heterodyne spectroscopy systems for the terahertz band. The current developmental status of terahertz-band HEB mixer receivers and their applications for spectroscopy and astronomy with ground-based, airborne, and satellite telescopes are presented. |
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1073 |
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Tol, J. van; Brunel, L.-C.; Wylde, R. J. |
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A quasioptical transient electron spin resonance spectrometer operating at 120 and 240 GHz |
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Journal Article |
| Year |
2005 |
Publication |
Rev. Sci. Instrum. |
Abbreviated Journal |
Rev. Sci. Instrum. |
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76 |
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7 |
Pages |
074101 (1 to 8) |
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Schottky, noise temperature |
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A new multifrequency quasioptical electron paramagnetic resonance (EPR) spectrometer is described. The superheterodyne design with Schottky diode mixer/detectors enables fast detection with subnanosecond time resolution. Optical access makes it suitable for transient EPR (TR-EPR) at 120 and 240 GHz. These high frequencies allow for an accurate determination of small g-tensor anisotropies as are encountered in excited triplet states of organic molecules like porphyrins and fullerenes. The measured concentration sensitivity for continuous-wave (cw) EPR at 240 GHz and at room temperature without cavity is 1013 spins/cm3 (15 nM) for a 1 mT linewidth and a 1 Hz bandwidth. With a Fabry-Perot cavity and a sample volume of 30 nl, the sensitivity at 240 GHz corresponds to [approximate]3×109 spins for a 1 mT linewidth. The spectrometer's performance is illustrated with applications of transient EPR of excited triplet states of organic molecules, as well as cw EPR of nitroxide reference systems and a thin film of a colossal magnetoresistance material. |
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Actually, noise spectral density is given (3e-19 W/Hz) |
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588 |
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Archer, J. W. |
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Multiple mixer, cryogenic receiver for 200-350 GHz |
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Journal Article |
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1983 |
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Rev. Sci. Instrum. |
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Rev. Sci. Instrum. |
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54 |
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10 |
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1371-1376 |
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Schottky, mixer, noise temperature |
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This paper describes a new 200–350-GHz dual polarization heterodyne radiometer receiver for radio astronomy applications. The receiver incorporates four pairs of cryogenically cooled Schottky-barrier diode single-ended mixers, each pair covering a 30–40-GHz subband of the full operating band. Each mixer, with its IF amplifier, is mounted in an individual cryogenic subdewar comprising a separate vcuum chamber and a cold stage, which may be readily thermally connected to or disconnected from the main refrigerator by a novel mechanical heat switch. A dual polarization LO diplexer is mounted on a rotary table above the subdewars. For band selection, the two diplexer rf output ports may be positioned over any of the four pairs of subdewars. The SSB receiver noise temperatues achieved are less than 500 K between 200 and 240 GHz, less than 800 K between 245 and 275 GHz and 1500 K at 345 GHz. |
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589 |
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Hirata, A.; Harada, M.; Nagatsuma, T. |
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120-GHz wireless link using photonic techniques for generation, modulation, and emission of millimeter-wave signals |
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Journal Article |
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2003 |
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J. of Lightwave Technology |
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21 |
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10 |
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2145-2153 |
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subterahartz terahertz THz communications |
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We present a wireless link system that uses millimeter-wave (MMW) photonic techniques. The photonic transmitter in the wireless link consists of an optical 120-GHz MMW generator, an optical modulator, and a high-power photonic MMW emitter. A uni-traveling carrier photodiode (UTC-PD) was used as the photonic emitter in order to eliminate electronic MMW amplifiers. We evaluated the dependence of UTC-PD output power on its transit-time limited bandwidth and its CR-time constant limited bandwidth, and employed a UTC-PD with the highest output power for the photonic emitter. As for the MMW generation, we developed a 120-GHz optical MMW generator that generates a pulse train and one that generates a sinusoidal signal. The UTC-PD output power generated by a narrow pulse train was higher than that generated by sinusoidal signals under the same average optical power condition, which contributes to reducing the photocurrent of the photonic emitter. We have experimentally demonstrated that the photonic transmitter can transmit data at up to 3.0 Gb/s. The wireless link using the photonic transmitter can be applied to optical gigabit Ethernet signals. |
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