| 1. |
- Jayasankar, Divya, 1994, et al.
(författare)
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Development of Supra-THz Schottky Diode Harmonic Mixers
- 2021
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Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - 2162-2027 .- 2162-2035. - 9781728194240 ; 2021-August
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Konferensbidrag (refereegranskat)abstract
- In this paper, we report the development of single-ended, Schottky diode-based harmonic mixers operating at 3.5 THz and 4.7 THz, respectively. Both mixers utilize a sub-micron size Schottky diode fabricated with circuit elements on a suspended 2 um-thick GaAs stripline circuit and then assembled in a waveguide split-block. The diode is closely integrated with the RF-waveguide, resulting in an electrically small and compact circuit. For the 3.5-THz, x6-harmonic mixer, a conversion loss of about 60 dB was measured at an intermediate frequency (IF) of 200 MHz. The predicted mixer performance versus dc bias agrees well with the measurements. Based on these results, the preliminary design and simulation results of a 4.7-THz, x8-harmonic mixer, are presented.
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| 2. |
- Auriacombe, Olivier, 1989, et al.
(författare)
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325 GHz and 650 GHz Dual-polarisation receivers Concept
- 2022
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Ingår i: 32nd International Symposium of Space Terahertz Technology, ISSTT 2022.
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Konferensbidrag (refereegranskat)abstract
- The integrated dual-polarisation receivers utilize a dual probe concept, efficiently integrating the antenna and MMIC package environment which allows for polarisation discrimination without the use of bulky and lossy external orthomode transducers. This concept increases the sensitivity of the instrument and reduces its size, enabling the development of future earth observation arrays. Omnisys Instruments AB (Sweden) and Chalmers University of Technology (Sweden) are working to demonstrate state-of-the-art dual polarisation capability with two integrated receiver modules at 325 GHz and 650 GHz.
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| 3. |
- Bevilacqua, Stella, 1981, et al.
(författare)
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Low noise MgB2 terahertz hot-electron bolometer mixers
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100:3
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Tidskriftsartikel (refereegranskat)abstract
- We report on low noise terahertz bolometric mixers made of MgB2 superconducting thin films. For a 10-nm-thick MgB2 film, the lowest mixer noise temperature was 600 K at 600 GHz. For 30 to 10-nm-thick films, the mixer gain bandwidth is an inverse function of the film thickness, reaching 3.4 GHz for the 10-nm film. As the critical temperature of the film decreases, the gain bandwidth also decreases, indicating the importance of high quality thin films for large gain bandwidth mixers. The results indicate the prospect of achieving a mixer gain bandwidth as large as 10-8 GHz for 3 to 5-nm-thick MgB2 films.
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| 4. |
- Bonmann, Marlene, 1988, et al.
(författare)
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Characterization of Graphene FET based 200 GHz Mixer and 1 GHz Amplifier Integrated on a Si Substrate
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- arises for new materials and technologies which can be used in the millimeter wave and terahertz wave regime. In this context, a receiver is an important component to be developed. It converts the received signals into useful information. A typical heterodyne receiver consists of an antenna, RF and IF filters, RF and IF amplifiers, and a mixer. The amplifiers and the mixer can be based on field effect transistors (FETs). To obtain high speed transistors the charge carrier mobility and velocity in the transistor channel should be high. Therefore, the 2D material graphene is an interesting material since it has a high room temperature charge carrier mobility and a high saturation velocity [1]. In previous works a 10 dB small-signal amplifier designed for 1 GHz [2] and a 185-215 GHz subharmonic resistive mixer [3] (designed for a center frequency at 200 GHz) based on graphene FETs (GFETs) have been demonstrated. The amplifier was further developed in [4] and the lumped inductor for matching used in [2] was replaced by an planar inductor. The measured and modeled gain for the two inductor types are shown in Fig. 1. The gain is reduced from 10 dBm to 5 dBm when using the planar inductor compared to the lumped inductor. The model shows that the gain can be increased to the designed gain of 10 dBm if the inductor resistance is reduced to Rs =5 by increasing the thickness of the gold conductor to 2 m. Additionally, the mixer design in [3] has been improved compared to the mixer design in [5] by decreasing the loss in the coplanar waveguid (CPW) circuit using air bridges. In this work, both, the amplifier and mixer are integrated together on a single silicon substrate and the characterization results are presented.
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| 5. |
- Hammar, Arvid, 1986, et al.
(författare)
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Wide-field off-axis telescope for the Mesospheric Airglow/Aerosol Tomography Spectroscopy satellite
- 2019
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 58:6, s. 1393-1397
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Tidskriftsartikel (refereegranskat)abstract
- We present the development of a compact ?/7.3 (?=35 mm) three-mirror reflective telescope for the atmospheric-research microsatellite Mesospheric Airglow/Aerosol Tomography Spectroscopy (MATS). The telescope design was driven by the end users’ need for a reflective wide-field (5.67°×0.91°) optic with high stray light rejection and six detection channels with separate image sensors, operating at wavelengths 270–772 nm. For the first time, a design method for wide-field off-axis telescopes—in which linear astigmatism is eliminated—was applied and tested in practice. Single-point diamond turning was used to produce two sets of 37–110 mm large free-form aluminum mirrors with surface figure errors and roughness values of 34–62 nm (RMS)/193–497 nm (PV) and 2.8–3.5 nm (RMS), respectively. A method that combines precise machining and geometry measurements (using a coordinate measuring machine) was employed to fabricate an aluminum structure to accurately position the mirrors without the need for manual alignment. The telescope was tested with a network of plate beamsplitters and filters, which define the spectral selection for the six detection channels. Imaging performance measurements were carried out using a reflective off-axis collimator, which projects imaging targets at infinite focus. A modulation transfer function (MTF) value of 0.45 at 20 lp/mm was measured at ∼760 nm (diffraction limit: 0.85) using a slanted edge target. By modeling the measured mirror surfaces in optical design software, a reoptimization of the mirror positions could be performed and an improved MTF of ∼0.75 at 20 lp/mm was predicted. The results demonstrate design- and building methods that can be utilized to make off-axis telescopes for a vast range of applications.
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| 6. |
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International Symposium on Terahertz Science and Technology between Japan and Sweden
- 2009
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Samlingsverk (redaktörskap) (refereegranskat)abstract
- The organisers and hosts warmly welcome you to the second International Symposium on Terahertz Science and Technology between Japan and Sweden, at Chalmers University of Technology, Göteborg, on November 18-20, 2009. The symposium is organised by the Department of Microtechnology and Nanoscience (MC2) at Chalmers. The aim is to create a forum and platform where researchers from the two countries can discuss latest results and trends in the field of terahertz science and technology. This year we have two keynote and 19 invited lectures divided into nine sessions.Sandwiched between the optical on the short wavelength side and radio on the long wavelength extreme, the terahertz (THz) or far-infrared has long been considered the last remaining scientific gap in the electromagnetic spectrum. The broad spectrum of THz applications has attracted researchers from different disciplines dealing with optics and photonics, microwave engineering and semiconductor physics. The role of this meeting is not only bridging the THz-gap but also strengthening the collaboration between Japan and Sweden.Chalmers is a university of technology in which research and teaching are conducted on a broad front within technology, natural science and architecture. Chalmers was founded in 1829. The university is named after the major benefactor, William Chalmers, one of the directors of the successful Swedish East India Company in Göteborg. Chalmers became an independent foundation in 1994. The meeting will be held at William Chalmers private residence, Chalmerska huset, which was erected in 1805-1807 and designed in a neoclassical style.The workshop is sponsored by the Swedish Research Council (VR) and MC2, Chalmers. We would like to thank these organisations for their support. We would also like to thank everyone who helped to arrange Japan-Sweden Terahertz Symposium (JSTS) 2009: the international steering committee for advice; the local organising committee: Eva Hellberg, Aleksandra Malko, Aik-Yean Tang, Dr. Sergey Cherednichenko, Dr. Biddut Banik and Prof. Dag Winkler for all practical efforts; Eriko Naito and Prof. Anders Karlsson at the Embassy of Sweden in Tokyo; our host Anna Bergius Hartman during the stay in Chalmerska huset; Dr. Göran Alestig for arranging the lab tour; invited speakers and everyone who attends or contributes to this event.On behalf of the local organising committee, we would like to welcome you all and wish you a pleasant and fruitful stay in Göteborg.Welcome!Jan Stake JSTS 2009 Chairman
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| 7. |
- Sobis, Peter, 1978, et al.
(författare)
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Compact 340 GHz Receiver Front-Ends
- 2009
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Ingår i: 20th International Symposium on Space Terahertz Technology. ; , s. 183-189
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Konferensbidrag (refereegranskat)abstract
- A compact 340 GHz room temperature receiver front-end has been developed consisting of a subharmonic Schottky diode mixer module with an integrated LNA. A novel sideband separation topology has been evaluated by using a pair of the developed mixers interconnected by external waveguide branch guide coupler hybrids for the LO and RF feedings and coaxial IF hybrids, measuring sideband suppression levels of 5 dB to 15 dB over the 315-365 GHz band.For efficient LO pumping of the sideband separating mixer, a novel high power LO chain based on a 5 x 34 GHz HBV quintupler (170 GHz LO source) has been developed with an ultra compact mechanical block housing, not much larger then a waveguide flange. We have also looked into a broadband medium LO power source consisting of a W-band active multiplier module, based on commercial MMIC chips from Hittite, followed by a medium power Schottky doubler from VDI.The demonstrated compact receiver front end has a considerably reduced size and weight owing to the high multiplication factor of the compact LO chain and mixer with integrated LNA. The novel sideband separating topology that uses 90 degree hybrids for both LO and RF resolves the standing wave issue of a previously proposed topology, in which a matched Y-junction was used as an RF hybrid and a branch guide coupler with a 45 degree differential line phase shifter at the output, was used for the LO feeding. The proposed topology improves both the sideband suppression and reduces the standing waves at the LO and RF ports.
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| 8. |
- Sobis, Peter, 1978, et al.
(författare)
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Membrane Integrated Asymmetric Dual E-plane Probe Ortho Mode Transducer at 424 GHz
- 2018
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Ingår i: ISSTT 2018 - 29th IEEE International Symposium on Space Terahertz Technology, Proceedings Book. ; , s. 186-186
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Konferensbidrag (refereegranskat)abstract
- We present a practical low loss GaAs membrane integrated ortho mode transducer (OMT) at 424 GHz composed of two orthogonal open ended E-plane probes in a circular waveguide. The proposed structure is suitable for building compact dual polarisation receivers in the lower THz range (~100 GHz – 1 THz) and is readily integrated directly to the first receiver element, in this case a subharmonic GaAs Schottky diode mixer, without any additional penalty in terms of loss or manufacturability. A 3-port OMT split block aluminium module, with rectangular WR-2.2 waveguide interfaces for the separated V/H polarisations and 375 μm diameter circular waveguide for the common V/H port has been designed and fabricated. The simulated nominal response of the membrane OMT reaches X-pol levels below 20 dB over 10% bandwidth with a worst case insertion loss of 0.3 dB. The simulated inter probe leakage (isolation) and circular waveguide reflected X-pol levels where around 20 dB. For the particular OMT test additional E-plane probe transitions were integrated on-chip to be able to couple the separated V/H polarisations to the rectangular waveguide test ports. Measurements on two circular waveguide interconnected back to back OMT modules using VDI WM-570 (WR-2.2) VNAX frequency extenders, show X-pol and isolation levels below 10 dB and return loss levels below 15 dB including effects of standing waves. Translated to a single OMT transition this corresponds to a X-pol and isolation of about 15 dB. The loss of a single OMT probe transition including the membrane circuit and circular waveguide loss was estimated to about 0.2 dB. The results look promising and the next step will be to test the integrated OMT concept in a 424.7 GHz dual polarization receiver currently being pre-developed by Omnisys Instruments AB for the ISMAR instrument.
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