| 1. |
- Belitsky, Victor, 1955, et al.
(författare)
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Superconducting microstrip line models at millimeter and sub-millimeter waves and their comparison
- 2003
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Ingår i: Proceedings of the 14th International Symposium on Space and Terahertz technology. ; , s. 456-475
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Konferensbidrag (refereegranskat)abstract
- Performance of superconductor — insulator - superconductor (SIS) tunnel junction mixers andtheir instantaneous input RF bandwidth are mostly depending on the integrated tunin g circuit used to resonate out SIS junction capacitance; Nb-based SIS mixers operate in the frequency range of about 80 - 1000 GHz and typically use microstrip-based integrated tuning circuitries.One of the major challenges in designing the tuning circuitry for SIS mixers is accuracy of models for superconducting microstrip line (SML). Modeling gives the only tool to solve the problem of designing SML-based circuits because for such high frequencies no direct measurements of a superconducting transmission line can be made with required high accuracy.However, creating an accurate model for such a superconducting transmission line is a challengeby itself. In the SML, produced usually by thin-film technology, the magnetic field penetrationdepth is comparable with the thicknesses of the dielectric and superconductors comprising theline. As a result the electromagnetic wave is propagated not only in the dielectric media but alsoinside the superconducting strip and ground electrodes constituting the SML. This createsdramatic changes in the transmission line behavior that should be carefully accounted byincluding the superconducting material properties into the modeling. Nb superconductor, as themost commonly exploited material, was used in this study for modeling of the superconductingmicrostrip though the same approach would work for any different BCS superconductingmaterial. The purpose of this paper is to introduce a new model for SML and compare it withpreviously suggested models and results of SML numerical simulation.
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| 2. |
- Dong, Bin, 1984, et al.
(författare)
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Optimization and Realization of Quadruple-ridge Flared Horn with New Spline-defined Profiles as a High-efficiency Feed over 4.6–24 GHz
- 2019
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 67:1, s. 585-590
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present a new optimization and realization of a quadruple-ridge flared horn (QRFH) as a feed for reflector antennas of the Square Kilometre Array (SKA) project. The QRFH has been numerically optimized by spline-defined profiles for both the ridges and the horn sidewall, with a conical cavity in the back-short for maximum aperture efficiency. The final aperture efficiency better than (for horizontal polarization) or around (for vertical polarization) 78% over 4.6–8 GHz, 70% over 8–15 GHz, 65% over 15–20 GHz and 60% over 20–24 GHz in the SKA offset-Gregorian dual-reflector antenna has been achieved. The realization of the horn has been carried out carefully by applying several new mechanical design solutions in order to guarantee the accurate positioning of the ridges, the feeding pins and a good electrical contact. The measured S11 is mostly better than -10 dB and the predicted aperture efficiency based on the measured far field patterns agrees well with the simulated result. System performance, such as the sensitivity and system noise temperature, are also estimated and presented.
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| 3. |
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| 4. |
- Meledin, Denis, 1974, et al.
(författare)
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APEX Band T2: A 1.25 – 1.39 THz Waveguide Balanced HEB Receiver
- 2008
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Ingår i: Proceedings of The 19th International Symposium on Space Terahertz Technology, Groningen, 28-30 April, 2008, ed. W. Wild, Space Research Organization of the Netherlands (SRON). ; part I, s. 162-166
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Konferensbidrag (refereegranskat)abstract
- A waveguide 1.25 - 1.39 THz Hot Electron Bolometer (HEB) balanced receiver was successfully developed, characterized and installed at the Atacama Pathfinder EXperiment (APEX) telescope. The receiver employs a quadrature balanced scheme using a waveguide 90-degree 3 dB RF hybrid, HEB mixers and a 180-degree IF hybrid. The HEB mixers are based on ultrathin NbN film deposited on crystalline quartz with a MgO buffer layer. Integrated into the multi-channel APEX facility receiver (SHeFI), the results presented here demonstrate exceptional performance; a receiver noise temperature of 1000 K measured at the telescope at the center of the receiver IF band 2-4 GHz, and at an LO frequency of 1294 GHz. Stability of the receiver is in line with the SIS mixer bands of the SHeFI, and gives a spectroscopic Allan time of more than 200 s at 1382 GHz with a noise bandwidth of 1 MHz.
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