| 1. |
- Jayasankar, Divya, 1994, et al.
(författare)
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4.7-THz Schottky Diode Harmonic Mixer: Design, Fabrication, and Performance Optimization
- 2024
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Ingår i: ISSTT 2024 - 33rd International Symposium on Space Terahertz Technology.
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Konferensbidrag (refereegranskat)abstract
- This paper focuses on the ongoing development of supra-THz harmonic mixers at Chalmers University of Technology. The planar, single-ended, x8-harmonic mixers based on Schottky-barrier diodes were realized on a 2-um GaAs substrate with integrated pyramidal horn. In contrast to our previous design with a diagonal horn, the new design addresses sensitivity to E-plane misalignment, which previously compromised mixer performance. The availability of THz harmonic frequency converters operating at ambient temperature is pivotal in realizing high-resolution THz heterodyne receivers.
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| 2. |
- Jayasankar, Divya, 1994, et al.
(författare)
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Design and Characterisation of a 3.5-THz Fundamental Schottky Mixer
- 2022
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Ingår i: 32nd International Symposium of Space Terahertz Technology, ISSTT 2022.
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Konferensbidrag (refereegranskat)abstract
- Mixers operating at ambient temperatures are essential for realisation of THz heterodyne receivers for long lifetime space missions. In this paper, we report the design, circuit and block fabrication, assembly and characterisation of a 3.5-THz fundamental Schottky diode mixer. Design of planar, integrated mixer circuit realised using a suspended stripline technology on a 2-µm GaAs substrate and video signal detection results are presented.
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| 3. |
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| 4. |
- Neumaier, Philipp, 1984, et al.
(författare)
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Molecular Spectroscopy With a Compact 557-GHz Heterodyne Receiver
- 2014
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 4:4, s. 469-478
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Tidskriftsartikel (refereegranskat)abstract
- We report on a heterodyne terahertz spectrometer based on a fully integrated 557-GHz receiver and a digital fast Fourier transform spectrometer. The receiver consists of a chain of multipliers and power amplifiers, followed by a heterostructure barrier varactor tripler that subharmonically pumps a membrane GaAs Schottky diode mixer. All sub-components are newly developed and optimized with regard to the overall receiver performance such as noise temperature, power consumption, weight and physical size. The receiver works at room temperature, has a double sideband noise temperature as low as 2000 K at a maximum power consumption of 4.5 W with an Allan time of 10 s and a sideband gain ratio of 0.52. The performance of the spectrometer is demonstrated by absorption spectroscopy of H2O and CH3OH with an instantaneous bandwidth of 1.5 GHz and a resolution of 183 kHz. Several pressure broadening parameters of methanol absorption lines were determined, that agree with other published data. Using the experimentally determined molecular parameters the CH3OH absorption spectrum could be modeled with very high precision.
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| 5. |
- Neumaier, Philipp, 1984, et al.
(författare)
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Molecular spectroscopy with a compact 557 GHz heterodyne receiver
- 2013
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Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - 2162-2027 .- 2162-2035.
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Konferensbidrag (refereegranskat)abstract
- In this work the results of spectroscopic and performance measurements with a compact heterodyne receiver in the frequency range between 520 and 590 GHz are presented.
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| 6. |
- Richter, Heiko, et al.
(författare)
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Frequency stabilization of 3.5-THz and 4.7-THz quantum-cascade lasers by a phase-locked loop
- 2022
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Ingår i: 32nd International Symposium of Space Terahertz Technology, ISSTT 2022.
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Konferensbidrag (refereegranskat)abstract
- We report on a phase-locked loop for quantum-cascade lasers operating at 3.5 and 4.7 THz. These frequencies are particularly relevant in atmospheric science and astronomy. The QCLs are locked to the multiplied output of a frequency synthesizer using a Schottky diode harmonic mixer. The resulting linewidths are in the order of a few Hz.
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| 7. |
- Richter, Heiko, et al.
(författare)
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Phase Locking of 3.5-THz and 4.7-THz Quantum-Cascade Lasers Using a Schottky Diode Harmonic Mixer
- 2021
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Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - 2162-2027 .- 2162-2035. ; 46
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Konferensbidrag (refereegranskat)abstract
- High frequency accuracy and stability are important requirements for local oscillators in terahertz heterodyne spectrometers. We report on a phase-locked loop for quantum-cascade lasers (QCLs) operating at 3.5 and 4.7 THz, two very important frequencies in atmospheric science and astronomy. The QCLs are locked to the multiplied output of a frequency synthesizer using a Schottky diode harmonic mixer.
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| 8. |
- Richter, Heiko, et al.
(författare)
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Phase-Locking of Quantum-Cascade Lasers Operating Around 3.5 THz and 4.7 THz with a Schottky-Diode Harmonic Mixer
- 2024
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - : IEEE Microwave Theory and Techniques Society. - 2156-342X .- 2156-3446. ; 14:3, s. 346-353
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Tidskriftsartikel (refereegranskat)abstract
- Quantum-cascade lasers (QCLs) are critical components for high-resolution terahertz spectroscopy, especially in heterodyne spectrometers, where they serve as local oscillators. For this purpose, QCLs with stable frequencies and narrow linewidths are essential since their spectral properties limit the spectral resolution. We demonstrate the phase-locking of QCLs around 3.5 THz and 4.7 THz in mechanical cryocoolers. These frequencies are particularly interesting for atmospheric research because they correspond to the hydroxyl radical and the neutral oxygen atom. The phase-locked loop is based on frequency mixing of the QCLs at 3.5 and 4.7 THz with the sixth and eighth harmonic, respectively, generated by an amplifier-multiplier chain operating around 600 GHz, with a Schottky diode harmonic mixer. At both frequencies we achieved a linewidth of the intermediate frequency signal of less than 1 Hz. This is about seven orders of magnitude less than the linewidth of the free running QCL.
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| 9. |
- Stake, Jan, 1971, et al.
(författare)
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TERACOMP
- 2011
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Ingår i: let´s embrace space. - 9789279197048 ; , s. 405-409
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Sub-millimetre wave or terahertz heterodyne receivers are key instruments for many space applications. For example, they are required for monitoring of the earth’s atmosphere or detection of molecules that might be tracers of life on other planets or moons. However, key components of these systems are currently supplied from outside Europe and performance as well as mass and power requirements often prohibit the implementation. The TeraComp project aims at developing European industrial level capability to design and manufacture terahertz front-end electronics based on high frequency Schottky diodes, Heterostructure Barrier Varactor (HBV) diodes and mHEMT MMICs for space and other applications. The prototype components will be integrated into a compact 557 GHz heterodyne receiver and evaluated for space instrument applications. The front-end demonstrator consists of a low noise 557 GHz subharmonic Schottky diode mixer, a 275 GHz Heterostructure Barrier Varactor frequency tripler and a 92 GHz mHEMT power amplifiers and a 15 to 92 GHz 6x multiplier as part of the local oscillator chain. This development will significantly contribute to mass and power reduction and it will improve the performance of terahertz heterodyne receivers. In addition, the dependence on critical technologies and capabilities from outside Europe for future space applications will be reduced.
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| 10. |
- Stockhausen, A., et al.
(författare)
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Adjustment of self-heating in long superconducting thin film NbN microbridges
- 2012
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Ingår i: Superconductor Science and Technology. - : IOP Publishing. - 0953-2048 .- 1361-6668. ; 25:3
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Tidskriftsartikel (refereegranskat)abstract
- The self-heating in long superconducting microbridges made from thin NbN films deposited on top of high silicon mesa structures was studied by analyzing the hysteresis current density j(H). We observed a more than twofold decrease of j(H) with increase in the ratio of the height of the Si mesa, h, to the width of the microbridge, W, from 0 to 24. We describe our experimental results using one-dimensional thermal balance equations taking into account disordered matter in our thin NbN films and limitations imposed on the phonon mean free path by the width of the Si mesa. In the framework of this model we obtain a good agreement between theory and experiment over a wide temperature range from 4.2 K up to the critical temperature T-C for all h/W ratios.
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