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- Belitsky, Victor, 1955, et al.
(författare)
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Terahertz Instrumentation For Radio Astronomy
- 2009
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Ingår i: International Symposium on Terahertz Science and Technology between Japan and Sweden. ; , s. 28-29
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Radio Astronomy was always a frontrunner in the demand on terahertz technology. Millimetre and sub-millimetre wave receivers operate at ground-based observatories for more than 20 years with real Terahertz instruments making its way to ground-based [1] and space-based observatories, e.g., Herschel HIFI, during last years.In this talk, we will look at the key requirements to the radio astronomy and environmental science terahertz receivers using heterodyne technology. The most promising and established technologies for high-resolution spectroscopy instrumentation will be discussed. Using results of the Group for Advanced Receiver Development for Onsala Space Observatory 20 m telescope, for Atacama Pathfinder Experiment (APEX) telescope and ALMA Project Band 5, we will illustrate the trends and achievements in the terahertz instrumentation for radio astronomy.
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| 4. |
- Nyström, Olle, 1979, et al.
(författare)
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Low-Noise Cryogenic Amplifier built using Hybrid MMIC-like / TRL Technique
- 2008
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Ingår i: GigaHertz Symposium, March 5-6, 2008, Göteborg.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- HEMT cryogenic low-noise amplifiers are an important part of instrumentation: the amplifiersuse as a front-end for different measurements and as IF amplifiers in heterodyne receivers.During last few years the low-noise limit has reached as low level as approximately 0.5 K/GHzfor GaAs [1] and 0.25 K/GHz for InP HEMT [2]. However, besides electrical performanceimprovement there were not many improvements on mass and dimension side of suchamplifiers as they were built based on standard TRL technology with discrete active andpassive components. Mass and dimensions are also very important for real applications. Whenultimate low-noise performance is placed in focus, pure MMIC technology seems to looseagainst design using discrete components. With this in view, pioneered work by E. F. Lauria,et. al. [3] have successfully demonstrated a design employing MMIC approach while usingdiscrete components and based on a microstrip on Cuflon with lumped bias network.Encouraged by this work, we propose a compact design of a 4-8 GHz cryogenic low noiseamplifier using a combination of standard TRL and lumped element technology to achieveboth ultimate noise performance over the specified band and a very compact size. In ourdesign, the size reduction of the amplifier is realized by selecting an alumina substrate with ahigh dielectric constant, (εr = 9.9), but also by taking advantage of the lumped networks in thematching and bias circuitries. Avoiding quarter wave transformers and instead use a lumpedelement design approach opens up for the possibilities to reach greater bandwidths andsimultaneously obtain a more compact design. In order to make optimum design, we haveperformed extensive simulations. Each amplifier stage has been simulated in Agilent EMDS,3D electromagnetic field simulation package, including the single layer capacitors, and thenimplemented in the ADS circuit simulations as an S-parameter file. Over the 4-8 GHz band, thesimulations predict noise temperature, Taverage 35 dB. The transistors selected for the design are commercial InP HEMT (HRL) chosendue to their excellent noise performance [2], but also for the very low power consumption,which is of great importance at cryogenic temperatures. All the components used in the RFsignalpath and in the bias circuits are mounted with conductive epoxy. Apart from the RFsignalpath, all components are interconnected via bond-wires. Fine tuning is done by adjustingthe length and loop heights of the bond-wires. At the conference we plan to report results ofmeasurement and characterization of the prototype amplifier.REFERENCES:[1] C Risacher, et. al., “Low Noise and Low Power Consumption Cryogenic Amplifiers forOnsala and Apex Telescopes”, Proceedings of Gaas 2004, October 2004, Amsterdam.[2] N. Wadefalk, et. al., “Cryogenic Wide-Band Ultra-Low Noise IF Amplifier Operating atUltra-Low DC-Power”, IEEE Transactions on Microwave Theory and Techniques, vol. MTT-51, no. 6 June 2003.[3] E. F. Lauria, et. al., “A 200-300 GHz SIS Mixer-Preamplifier with 8 GHz IF Bandwidth”,2001 IEEE International Microwave Symposium, Phoenix, AZ, May 2001.
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| 5. |
- Nyström, Olle, 1979
(författare)
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Design, Characterization, and Calibration of Low-Noise Terahertz Receivers
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is focused on the field of instrumentation for radio-astronomy and atmospheric science, and specifically deals with problems such as optical design and its verification, horn antennas and receiver optics’ components, different aspects of measurement systems in order to characterize low-noise THz receivers, and its calibration techniques.Ultra low-noise Terahertz receivers, used in radio-astronomy, are typically coupled to the telescope system through relay optics that provides guiding of the signal to the receiver frontend with minimal loss. Any misalignments, beam truncation, and distortion in the optical system will introduce losses and degrade the overall noise performance of the system. It is therefore critical that the optical design could be verified through measurements. In this thesis the author presents a vector beam measurement system to create possibilities to accurately characterize the optical performance of multi-band receivers over a very wide frequency range. The developed beam measurement system employs a novel circuitry allowing the use of a single reference source, different frequency harmonics of which allow to generate the required RF and LO signals yielding the desired IF, while obtaining perfect phase-coherence and initial phase-noise cancellation. An advantage of such wideband measurement system is that it could be used in different projects, nearly independent on frequency. Implementation of the measurement system, covering 163 GHz to 500 GHz, for the APEX receiver - Swedish Heterodyne Facility Instrument (SHeFI) - and the ALMA Band 5 receiver cartridge is described. Apart from optical characterization, noise-, sideband rejection, amplitude- and phase stability, and gain saturation measurements of the receivers are the measurements performed within the very same measurement setup. The measurement setup includes all necessary hardware and achieves largely automatic measurements with in-built optimization procedures. Another part of the thesis describes the author’s work on design of horn antennas. The feed horn is one of the most critical components in an optical system since it has direct impact on the total system performance. Two horn designs are presented in this thesis, one profiled corrugated feed horn, where particle swarm optimization (PSO) was successfully employed in the design procedure. The PSO drastically reduces the computational time and provides a robust optimization in terms of finding global optimum. A second horn design, implemented within PHOCUS, the Swedish sounding rocket project, is used for two water vapour radiometers, 183 GHZ and 557 GHZ. These antennas are based on the Potter horn and designed to provide FWHM of 5° without any additional focusing elements. Apart from the antenna design, two different calibration systems for both the 183 GHz and the 557 GHz radiometers on the PHOCUS sounding rocket have been suggested, designed, verified and implemented. The calibration systems shall meet challenging requirements associated with the rocket platform such as acceleration, shock, vibrations, limited space, and short flight time.
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- Nyström, Olle, 1979
(författare)
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THz Vector Beam Measurement System for APEX Instrument SHeFI and Microwave Cryogenic Low Noise Amplifier Design
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This licentiate thesis describes results of the author’s work on development of THz vector beam measurement system and microwave cryogenic low-noise amplifier.The first part, and the main focus, of the thesis covers the vector beam measurement system for frequency range 210-500 GHz developed to characterize/verify the cold opticsof the APEX instrument SHeFI. The measurement system, based on a novel design employing combination of a single frequency source, comb-generator, and direct multiplication signal sources, is described in detail. The system configuration allows very narrow detection bandwidth giving the advantage of high dynamic range. With minor rearrangements, the same setup is used to characterize the three first receiving bands of SHeFI, covering the frequency range 211-500 GHz.In the first part of the thesis, the results from the measurements are presented and complemented with an extensive error analysis of the measurement setup. Additionally, we present results of the scalar beam characterization at 1334 GHz. One chapter of thethesis is also dedicated to describe the installation procedure at the telescope, where results from the first telescope pointing tests are presented. The second part of the thesis deals with the development of a three stage low-noise cryogenic amplifier based on InP-High Electron Mobility Transistors HEMTs for the frequency range 4-8 GHz. The design employs a combination of standard TRL, based onalumina substrate, and lumped element technology to achieve both ultimate noise performance over the specified band and a very compact size. Simulation results are presented together with the first preliminary measurement results (employing GaAs HEMTs).
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