| 1. |
- de Graauw, Th., et al.
(author)
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The Herschel-Heterodyne Instrument for the Far-Infrared (HIFI)
- 2010
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 518, s. L6-
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Journal article (peer-reviewed)abstract
- Aims: This paper describes the Heterodyne Instrument for the Far-Infrared (HIFI) that was launched onboard ESA's Herschel Space Observatory in May 2009. Methods: The instrument is a set of 7 heterodyne receivers that are electronically tuneable, covering 480-1250 GHz with SIS mixers and the 1410-1910 GHz range with hot electron bolometer (HEB) mixers. The local oscillator (LO) subsystem comprises a Ka-band synthesizer followed by 14 chains of frequency multipliers and 2 chains for each frequency band. A pair of auto-correlators and a pair of acousto-optical spectrometers process the two IF signals from the dual-polarization, single-pixel front-ends to provide instantaneous frequency coverage of 2 × 4 GHz, with a set of resolutions (125 kHz to 1 MHz) that are better than 0.1 km s-1. Results: After a successful qualification and a pre-launch TB/TV test program, the flight instrument is now in-orbit and completed successfully the commissioning and performance verification phase. The in-orbit performance of the receivers matches the pre-launch sensitivities. We also report on the in-orbit performance of the receivers and some first results of HIFI's operations. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
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| 2. |
- Kollberg, Erik, 1937, et al.
(author)
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Impedance of Hot-Electron Bolometer Mixers at Terahertz Frequencies
- 2011
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In: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 1:2, s. 383-389
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Journal article (peer-reviewed)abstract
- This paper discusses the current distribution in thin-film devices, especially in a hot-electron bolometer (HEB) mixer at terahertz frequencies, and the consequences of different current distributions on the device impedance. We first present an approximate analytical model from which we derive a proposed rule of thumb for deciding when the film is thin enough to support a current distribution that is uniform in the transverse direction. We then verify this rule by performing electromagnetic simulations. Our conclusion is that the current distribution in thin films with a relatively high DC resistivity and small film thickness with respect to the skin depth is essentially uniform up to 8 THz. These results are crucial, e.g., for understanding radiation coupling between an HEB and an antenna and indispensable when analyzing detectors and receivers based on bolometric properties of thin films.
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| 3. |
- Tavakoli Dastjerdi, Mohammad Hadi, 1984, et al.
(author)
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InGaAs/InAlAs/AlAs Heterostructure Barrier Varactors on Silicon Substrate
- 2011
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In: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 32:2, s. 140-142
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Journal article (peer-reviewed)abstract
- We present the results of a study on epitaxial transferof InP-based heterostructure barrier varactor (HBV) materials onto a silicon substrate employing the low-temperature plasma activated bonding technique. The test diodes fabricated on the bonded samples exhibit symmetric electrical characteristics, over the temperature range of 25 ˚C–165 ˚C, and show no degradation compared to previously reported InP-based diodes. Moreover, the onset temperature for debonding, the effective barrier height extracted from the measured data, and the maximum voltage of the HBVs for a current density of 100 A/cm2 were extracted to be 260 ˚C, 0.56 eV, and 10.5 V, respectively.
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| 4. |
- Zhang, W., et al.
(author)
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Quantum noise in a terahertz hot electron bolometer mixer
- 2010
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 96:11, s. 111113 -
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Journal article (peer-reviewed)abstract
- We have measured the noise temperature of a single, sensitive superconducting NbN hot electron bolometer (HEB) mixer in a frequency range from 1.6 to 5.3 THz, using a setup with all the key components in vacuum. By analyzing the measured receiver noise temperature using a quantum noise (QN) model for HEB mixers, we confirm the effect of QN. The QN is found to be responsible for about half of the receiver noise at the highest frequency in our measurements. The beta-factor (the quantum efficiency of the HEB) obtained experimentally agrees reasonably well with the calculated value.
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