| 1. |
- Carlsson, Erik F., 1968, et al.
(författare)
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Arrangement and method relating to filtering of signals
- 2000
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Patent (övrigt vetenskapligt/konstnärligt)abstract
- A superconducting notch or band reject filter arrangement includes a superconducting dielectric resonator and a waveguide arrangement including a microstrip line to which the resonator is connected. The resonator is a parallel-plate resonator with a chip of a non-linear dielectric material device on which superconductors are arranged and the waveguide arrangement includes a contact device or a coupling device, the resonator being connected to the contact device of the waveguide arrangement in such a way that electric contact is provided, and the filter arrangement is frequency tuneable. Through the arrangement, the insertion losses are low
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| 2. |
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| 3. |
- Gevorgian, Spartak, 1948, et al.
(författare)
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Lower order modes of YBCO/STO/YBCO circular disk resonators
- 1996
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9480 .- 1557-9670. ; 44:10, s. 1738 - 1741
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Tidskriftsartikel (refereegranskat)abstract
- Lower order modes in a single crystal strontium titanate (STO) circular disk resonator are studied experimentally. Superconducting epitaxial YBCO films form the parallel-plates of the resonator. Due to the extremely high dielectric constant of STO, the electric fields are concentrated between the plates, while there is a substantial magnetic fringing field which affects both the resonant frequencies, Q-factors, and tunability of all modes, especially the TM110 and TM210
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| 4. |
- Alderman, Byron, et al.
(författare)
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A New Pillar Geometry for Heterostructure Barrier Varactor Diodes
- 2001
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Ingår i: 12th International Symposium on Space Terahertz Technology. ; , s. 330-339
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Konferensbidrag (refereegranskat)abstract
- We report on a novel diode geometry, with reduced thermal resistance, for Heterostructure Barrier Varactor, HBV, diodes. The pillar geometry presented here involves the complete removal of the substrate, electrical contacted is made by the forward and reverse side processing of metallic pillars. We propose that there is a limit to the maximum number of barriers that can be used to increase the power capability of a HBV. An analytical model has been developed to study these effects. In considering the case of a perfect thermal heat sink the limit is found to be fourteen, in applying this model to the new pillar structure this is reduced to six.
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| 5. |
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| 6. |
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| 7. |
- Cherednichenko, Serguei, 1970, et al.
(författare)
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Hot-electron bolometer terahertz mixers for the Herschel Space Observatory
- 2008
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 79:034501, s. 034501-1 to 034501-10-
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Tidskriftsartikel (refereegranskat)abstract
- We report on low noise terahertz mixers (1.4–1.9 THz) developed for the heterodyne spectrometer onboard the Herschel Space Observatory. The mixers employ double slot antenna integrated superconducting hot-electron bolometers (HEBs) made of thin NbN films. The mixer performancewas characterized in terms of detection sensitivity across the entire rf band by using a Fourier transform spectrometer (from 0.5 to 2.5 THz, with 30 GHz resolution) and also by measuring the mixer noise temperature at a limited number of discrete frequencies. The lowest mixer noise temperature recorded was 750 K (double sideband (DSB)) at 1.6 THz and 950 K DSB at 1.9 THz local oscillator (LO) frequencies. Averaged across the intermediate frequency band of 2.4–4.8 GHz,the mixer noise temperature was 1100 K DSB at 1.6 THz and 1450 K DSB at 1.9 THz LO frequencies. The HEB heterodyne receiver stability has been analyzed and compared to the HEBstability in the direct detection mode. The optimal local oscillator power was determined and found to be in a 200–500 nW range.
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| 8. |
- Cherednichenko, Serguei, 1970, et al.
(författare)
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The Direct Detection Effect in the Hot-Electron Bolometer Mixer Sensitivity Calibration
- 2007
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 55:3, s. 504-510
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Tidskriftsartikel (refereegranskat)abstract
- We investigate an error in the noise temperature measurements of the hot-electron bolometer mixers caused by the so-called "direct detection effect". The effect originates in the changing of the mixer parameters when the mixer is loaded on calibration black body sources at different temperatures (300 and 77 K). A correction factor was obtained from the mixer output power versus the bias current dependence, measured by: 1) the local oscillator (LO) power tuning: 2) mixer heating: and 3) application of an external RF source. Furthermore, the direct detection effect was assessed by elimination of the heterodyne response using a LO frequency, which is far off the mixer RF band. We show that the direct detection effect can be mitigated by using an isolator between the mixer and the IF amplifier.
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| 9. |
- de Graauw, Th., et al.
(författare)
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The Herschel-Heterodyne Instrument for the Far-Infrared (HIFI)
- 2010
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 518, s. L6-
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Tidskriftsartikel (refereegranskat)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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| 10. |
- Deleniv, Anatoli, 1969, et al.
(författare)
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Experimental characterization of the 3rd order nonlinearities in thin film parallel-plate ferroelectric varactors
- 2007
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Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 1424406889 ; 2, s. 683-686
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Konferensbidrag (refereegranskat)abstract
- The 3rd order nonlinearities in parallel-plate ferroelectric varactors based on thin Ba0.25Sr0.75TiO3 epitaxial films are characterized in wide temperature range. Both, the generated 3rd order harmonic and 3rd order intermodulation products are measured experimentally. The 3rd harmonic IP3 at room temperature is measured to be 35dBm and is favorable as compared to semiconductor competitors. The good agreement between harmonic balance simulation and measured data indicate that the measured low frequency C-V is adequate for accurate design of nonlinear components.
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| 11. |
- Dillner, Lars, 1968, et al.
(författare)
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Analysis of Symmetric Varactor Frequency Multipliers
- 1997
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Ingår i: Microwave and Optical Technology Letters. ; 15:1, s. 26-29
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Tidskriftsartikel (refereegranskat)abstract
- We investigate efficiency limitations of frequency multipliers with the use of a simple model for symmetric varactors. Our calculations show that the conversion efficiency is improved for a C(V) shape with large nonlinearity at zero volt bias. For quintuplers, the optimal embedding impedance at the third harmonic is an inductance in resonance with the varactor diode capacitance.
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| 12. |
- Dillner, Lars, 1968, et al.
(författare)
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Frequency Multiplier Measurements on Heterostructure Barrier Varactors on a Copper Substrate
- 2000
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Ingår i: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 21:5, s. 206-208
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Tidskriftsartikel (refereegranskat)abstract
- We have fabricated heterostructure barrier varactors (HBV) on a copper substrate, which offers reduced spreading resistance, and improved thermal conductivity compared to an InP substrate. The devices are fabricated without degrading the electrical characteristics. The three-barrier HBV material grown by MOVPE has a leakage current of only 0.1 mu A/ mu m/sup 2/ at 19 V. The maximum capacitance is 0.54 fF/ mu m/sup 2/. In a frequency tripler experiment a maximum output power of 7.1 mW was generated at 221 GHz with a flange-to-flange efficiency of 7.9%.
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| 13. |
- Dillner, Lars, 1968, et al.
(författare)
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Heterostructure Barrier Varactor Multipliers
- 2000
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Ingår i: GAAS 2000. - 0862132223 ; 1, s. 197-200
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Konferensbidrag (refereegranskat)abstract
- The Heterostructure Barrier Varactor (HBV) diode and its application in frequency multipliers is reviewed. Different material systems and HBV models are described. Multiplier performance versus diode parameters and some practical multiplier designs are discussed as well. The best result until now is an efficiency of 12% and an output power of 9 mW at an output frequency of 250 GHz.
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| 14. |
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| 15. |
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| 16. |
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| 17. |
- Dillner, Lars, 1968, et al.
(författare)
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High Efficiency HBV Multipliers for Millimetre Wave Generation
- 2000
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Ingår i: the XIII International Conference on Microwaves, Radar and Wireless Communications. - 8390666235 ; 3, s. 47-54
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Konferensbidrag (refereegranskat)abstract
- We describe the heterostructure barrier varactor (HBV) diode and its application in frequency multipliers. Different material systems and HBV models are described. In a frequency tripler experiment a maximum output power of 7.1 mW was generated at 221 GHz with a flange-to-flange efficiency of 7.9%.
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| 18. |
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| 19. |
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| 20. |
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| 21. |
- Emadi, Arezoo, 1977, et al.
(författare)
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High power HBV multipliers for F- and G- band applications
- 2004
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Ingår i: IRMMW 2004/THz 2004 / M. Thumm, W. Wiesbeck. - 0780384903 ; , s. 319-320
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Konferensbidrag (refereegranskat)abstract
- Progress and realisation of applications in the 100-240 GHz region is inhibited by the lack of high-power sources. Therefore, in an effort to reach watts of output power, we have tailored devices, circuits, materials, and design and fabrication methods for improved thermal management and high overall conversion efficiencies.
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| 22. |
- Fu, Ying, 1964, et al.
(författare)
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AlGaAs/GaAs and InAlAs/InGaAs Heterostructure Barrier Varactors
- 1997
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 82:11, s. 5568-5572
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Tidskriftsartikel (refereegranskat)abstract
- By the Schrödinger and Poisson equations, we have theoretically investigated AlGaAs/GaAs and InAlAs/InGaAs single barrier varactors. The energy band structure, carrier distribution, and conduction current are fully exploited for varactor design. We have explained the experimental current-voltage and capacitance-voltage measurements very well. A simple analytical model for energy band structure is derived based on the Schrödinger and Poisson equation calculation. It is found that a barrier structure of 3 nm Al0.3Ga0.7As/3 nm AlAs/3nm Al0.3Ga0.7As for an Al0.3Ga0.7As/GaAs varactor and a barrier structure of 8 nm In0.52Al0.48As/3 nm AlAs/8 nm In0.52Al0.48As for In0.52Al0.48As/In0.47GaAs are optimal for minimal conduction currents.
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| 23. |
- Fu, Ying, 1964, et al.
(författare)
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Capacitance Analysis for AlGaAs/GaAs and InAlAs/InGaAs Heterostructure Barrier Varactor Diodes
- 1998
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 83:3, s. 1457-1462
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Tidskriftsartikel (refereegranskat)abstract
- By self-consistently solving Schro¨dinger and Poissons equations, we have investigated the capacitances of AlGaAs/GaAs and InAlAs/InGaAs heterostructure barrier varactors. When compared with semiclassical particle model, quantum mechanics show that the maximal capacitance of the varactor is saturated when the spacer and barrier are thin. When the spacer and barrier are very thick, both the quantum mechanics and semiconductor particle approach result in the same conclusion, namely, the maximal capacitance is inversely proportional to the sum of the spacer and barrier thicknesses. We have also shown that the maximal capacitance increases for high carrier effective mass.
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| 24. |
- Fu, Ying, 1964, et al.
(författare)
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Carrier conduction through the quantum barrier in a heterostructure barrier varactor Induced by an AC-Bias
- 2000
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Ingår i: Superlattices and Microstructures. ; 28:2, s. 135-141
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Tidskriftsartikel (refereegranskat)abstract
- By solving the time-dependent Schrodinger equation, we have studied the quantum transport of a wavepacket in a GaAs/A1GaAs heterostructure barrier varactor (HBV) diode induced by an ac bias. The current conduction of a wavepacket is complicated due to the superposition of many different stationary states. When the oscillating frequency of the external bias is relatively low, the motion of the wavepacket follows the electric field induced by the external bias. When the frequency is too high (over 1000 GHz for the GaAs/A1GaAs HBV structure under investigation), the wavepacket becomes effectively confined by the oscillating bias, and the conduction current is significantly reduced.
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| 25. |
- Gevorgian, Spartak, 1948, et al.
(författare)
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Analytic approximation for open-end capacitance in symmetric coplanar-strip waveguides
- 2001
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 37:20, s. 1226 - 1228
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Tidskriftsartikel (refereegranskat)abstract
- Conformal mapping and partial capacitance technique are used to derive simple and accurate closed form approximations for open-end capacitance in a symmetric coplanar-strip waveguide.
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