| 11. |
- Billade, Bhushan, 1982, et al.
(författare)
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Performance of the first ALMA Band 5 production cartridge
- 2011
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Ingår i: Proceedings of the 22nd International Symposium on Space Terahertz Technology, April 26-28th, 2011 - Tucson, Arizona, USA. ; , s. 56-56
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Konferensbidrag (refereegranskat)abstract
- We present performance of the first ALMA Band 5 production cartridge, covering RF frequencies from 163 GHz to 211 GHz. ALMA Band 5 is a dual polarization, sideband separation (2SB) receiver based on all Niobium (Nb) SuperconductorInsulator-Superconductor (SIS) tunnel junction mixer, providing 16 GHz of instantaneous RF bandwidth for the astronomy observations. The 2SB mixer for each polarization employs a quadrature layout. The sideband separation occurs at the output of the IF hybrid that has integrated bias-T for biasing the mixers, and is produced using superconducting thin film technology. Experimental verification of the Band 5 cold cartridge performed together with warm cartridge assembly, confirms the system noise temperature below 45 K, less than five quantum noise (5 hf/k) over most of the RF band, which is to our knowledge, the best results at these frequencies. The measurement of the sideband rejection indicates that the sideband rejection better than 10 dB over 90% of the observational band.
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| 12. |
- Billade, Bhushan, 1982, et al.
(författare)
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Superconducting 4–8 GHz IF Hybrid for Low Noise mm-Wave Sideband Separation SIS Receiver
- 2012
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Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 22:11, s. 589-591
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Tidskriftsartikel (refereegranskat)abstract
- We present the design and performance of a superconducting 90 degree hybrid covering a full octave bandwidth from 4 to 8 GHz. The hybrid is designed using the Lange coupler layout. The novel features of this quadrature hybrid include superconducting niobium (Nb) transmission lines, air bridges to connect the fingers of the coupler and a bias-T integrated with the coupler. Our simulations indicate that the amplitude imbalance of the designed hybrid is less than 0.8 dB over the entire 4–8 GHz band with negligible phase imbalance.
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| 13. |
- Desmaris, Vincent, 1977, et al.
(författare)
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Design, simulations and optimization of micromachined Golay-cell based THz sensors operating at room temperature
- 2009
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Ingår i: Procedia Chemistry - Proceedings of the Eurosensors XXIII conference. ; 1:1, s. 1175-1178
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Konferensbidrag (refereegranskat)abstract
- An innovative wideband micro-machined terahertz (THz)sensor operating at room temperature is presented. By means of 3D finite element method (FEM) simulations, the original design of M. Golay was miniaturized and modified by the introduction of a second absorbing membrane providing simultaneously an inherently integrated capacitive read-out. With a help of advanced multi-objective design tools, the sensor design was optimized in terms of linear dimensions, material’s electrical and mechanical properties. Feasibility of the final structure and its tolerance to parameters variation during the fabrication was assessed through a Monte-Carlo analysis. The optimized sensor promises a bandwidth of 3.5 THz (0.5-4THz).
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| 14. |
- Ermakov, Andrey, 1960, et al.
(författare)
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Broken-step Phenomenon in SIS Mixers
- 2016
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Ingår i: 27th International Symposium on Space Terahertz Technology, ISSTT 2016, Nanjing, China.
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Konferensbidrag (refereegranskat)abstract
- In this paper, we discuss a “broken step” phenomenonin an SIS mixer. This phenomena was observed in the production version of the SIS mixers, designed for the 159-211 GHz RF band,being used for the construction of the ALMA Band 5 receiver The broken step typically appears at LO frequencies above 180 GHz and manifests itself as a sharp onset in the DC current at the middle of the quasiparticle step. Correspondingly, this affects the mixer IF response in a way that is similar to the Josephson step but is however of a different nature. Such behaviour affects the SIS mixer dynamic range and complicates the tuning of the 2SB mixer to optimize its performance, for both the receiver noise as well as the sideband rejection. In this paper, we describe results of a few experiments which were performed to understand this undesirable phenomenon.
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| 15. |
- Garrett, John D., et al.
(författare)
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A Nonlinear Transmission Line Model for Simulating Distributed SIS Frequency Multipliers
- 2020
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 10:3, s. 246-255
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Tidskriftsartikel (refereegranskat)abstract
- Superconductor/insulator/superconductor (SIS) jun-ctions have extremely nonlinear electrical properties, which makes them ideal for a variety of applications, including heterodyne mixing and frequency multiplication. With SIS mixers, the SIS junctions normally have circular cross sections, but they can also be fabricated in the form of microstrip transmission lines, known as distributed SIS junctions (DSJs). By using a DSJ as an open-circuit stub, it is possible to create a large SIS junction with a low effective input reactance. This is beneficial for SIS frequency multipliers because their output power is proportional to the area of the junction. It is challenging, however, to simulate the behavior of DSJs because they have to be modeled as transmission lines and the model has to take into account the quasiparticle tunneling current, which is a nonlinear function of the ac voltage. In this article, we present a new nonlinear transmission line model to accurately describe the behavior of DSJs and to simulate the performance of distributed SIS frequency multipliers (DSMs). This model is compared to experimental data from a recent DSM device and good agreement is found between the dc tunneling currents and the output powers at the second harmonic. Based on this success, an improved DSM design is proposed that has a higher output power and a higher conversion efficiency than previous designs. © 2011-2012 IEEE.
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| 16. |
- Garrett, John, et al.
(författare)
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Spectral Domain Simulation of SIS Frequency Multiplication
- 2017
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Ingår i: 28th International Symposium on Space Terahertz Technology. ; 2017-March
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Konferensbidrag (refereegranskat)abstract
- In this paper, we compare simulations to experimental results for a new SIS frequency multiplier. To simulate these devices, we developed software based on spectral-domain analysis, which is ideal for simulating higher-order harmonics such as those present in a multiplier. In addition, we included the embedding circuit and interpolated the experimental I-V curve to allow the simulation to capture the experimental system as closely as possible. For the experimental data, results were taken from a new SIS frequency multiplier that has recently been developed at the Chalmers University of Technology. Previously, these experimental results were compared to simulations based on Tucker theory. Here, we compare these results to spectral-domain simulations. Qualitatively, the inclusion of embedding impedances and the use of spectral-domain analysis improves the agreement between simulation and experiment. The software can now be used to design multipliers with high output power and high conversion efficiency
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| 17. |
- Krause, Sascha, 1989, et al.
(författare)
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Noise and IF Gain Bandwidth of a Balanced Waveguide NbN/GaN Hot Electron Bolometer Mixer Operating at 1.3 THz
- 2018
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Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 8:3, s. 365-371
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present the comprehensive characterization of a waveguide balanced phonon-cooled NbN hot electron bolometer (HEB) mixer on aGaNbuffer-layer operating at approximately 1.3 terahertz (THz). The measured uncorrected double sideband noise temperature was as low as 750 K at 1 GHz intermediate frequency (IF) and 900 K at 4 GHz IF, respectively, and suggests a noise bandwidth of 7 GHz. Moreover, the IF gain bandwidth of the HEB itself was deduced from a mixing experiment with a second monochromatic THz signal source and has shown a 3 dB roll-off at 5.5 GHz. The contribution of the HEB mixer on the overall receiver noise temperature was determined to be in the order of 300 K or 5 hf/k considering losses in the RF transmission path and the waveguide components as well as accounting for the receiver conversion loss, which was deduced from the U-factor method. The achieved performance sets a new benchmark for futureTHz instruments and emphasizes the technological readiness of waveguide-based NbN HEB mixers employing a GaN buffer-layer featuring significantly improved IF bandwidth without compromising on the receiver’s noise temperature.
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| 18. |
- Marouf Rashid, Hawal, 1982, et al.
(författare)
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Compact wideband passive and active component chips for radio astronomy instrumentation
- 2019
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Ingår i: ISSTT 2019 - 30th International Symposium on Space Terahertz Technology, Proceedings Book. ; , s. 50-56
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Konferensbidrag (refereegranskat)abstract
- In the 2SB receivers, the rejection ratio is determined among other factors by the performance of the quadrature hybrids. We have developed and fine‐tuned components that intended to be used in the IF chain and meet the requirements for new generation of compact wideband 2SB receivers. We present here the design and characterization of three multi‐section compact wideband 3 dB quadrature couplers (coupled line coupler – Lange coupler–coupled line coupler). Specifically, the miniaturized 3‐section hybrid chip made using thin‐film technology utilizes gold plated transmission lines and air bridges to connect the fingers of the Lange coupler (middle section The hybrids were designed to have the amplitude and phase imbalance better than 0.6 dB and ±3° respectively over a 3.5-12.5 GHz and 4-16 GHz frequency bands. Experimental verification of the assembly at 293 K and 4 K shows very good agreement between the measurements and simulations. Additionally, we demonstrate the suitability of the miniature hybrid chips, by implementing them in a balanced amplifier designed using a modular approach, which demonstrated promising results.
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| 19. |
- Marouf Rashid, Hawal, 1982, et al.
(författare)
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Design and simulations of a micromachined Golay-cell based THz sensors for room temperature imaging applications
- 2010
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Ingår i: 35th International Conference on Infrared Millimeter and Terahertz Waves (IRMMW-THz) 2010. - 9781424466559 ; , s. 1-2
-
Konferensbidrag (refereegranskat)abstract
- A novel broadband THz microsensor for room temperature imaging applications is presented. The sensor's response time is optimized by tuning its structural design, using Monte-Carlo and transient FEM simulations. The optimized and robust sensor shows a 3.5 THz bandwidth (0.5–4THz) and a response time of ~40ms, suitable for real time radio visualization.
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| 20. |
- Marouf Rashid, Hawal, 1982, et al.
(författare)
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Design of Wideband Waveguide Hybrid With Ultra-Low Amplitude Imbalance
- 2016
-
Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 6:1, s. 83-90
-
Tidskriftsartikel (refereegranskat)abstract
- We present a design and synthesis procedure for a new 90 ° waveguide hybrid with ultra-low amplitude imbalance. This novel hybrid design is based on Reed's multiple branch waveguide hybrid. The primary feature of this quadrature hybrid design is the introduction of a controllable ripple in the operational band by, firstly changing the heights of the input and output branches and, secondly, by introducing three waveguide-height discontinuity sections placed symmetrically in the main waveguide. This layout allows ultra-low amplitude imbalance over a wide operational band. At the same time, it permits a greater input/output branch height as compared to the Reed's 5-branch waveguide hybrid, which should ease fabrication for short-mm and sub-mm wavelengths. This design concept is demonstrated through a 90 ° waveguide hybrid for the 159-216 GHz band (30% fractional bandwidth). Our simulations indicate that the amplitude imbalance of the hybrid is better than 0.2 dB over the most of the 159-216 GHz band with a phase imbalance better than ±4°. Experimental verification of the hybrid shows excellent agreement with the simulations.
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