| 21. |
- Nyström, Olle, 1979, et al.
(författare)
-
A Vector Beam Measurement System for 211-275 GHz
- 2006
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Ingår i: Proceedings EuCAP 2006, Nice, France, 6-10 November 2006, (ESA SP-626, October 2006). - 9290929375
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Konferensbidrag (refereegranskat)abstract
- In this paper, we describe a novel vector measurement system for the characterization of Gaussian beams and present test results for mm-wave, 211-275 GHz, receiver optics alignment. The measurement setup allows a simpler design without any PLLs and employs a combination of a single frequency source, comb-generator, and direct multiplication LO and signal sources. The system takes advantage of different harmonics to generate the required RF and LO signals yielding the desired IF frequency while obtaining perfect phase-coherence and initial phase-noise cancellation. One of the additional advantages of the suggested measuring scheme is that it allows such design that it has the potential to cover different mm and sub-mm bands by only replacing two filters and the LO multiplication unit. For example, we plan to use the same setup, with mentioned modifications, for the frequency bands 275-370 GHz and 385-500 GHz.
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| 22. |
- Nyström, Olle, 1979
(författare)
-
Design, Characterization, and Calibration of Low-Noise Terahertz Receivers
- 2011
-
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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| 23. |
- Nyström, Olle, 1979, et al.
(författare)
-
PHOCUS radiometer
- 2012
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 5:6, s. 1359-1373
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Tidskriftsartikel (refereegranskat)abstract
- PHOCUS - Particles, Hydrogen and Oxygen Chemistry in the Upper Summer Mesosphere is a Swedish sounding rocket experiment, launched in July 2011, with the main goal of investigating the upper atmosphere in the altitude range 50-110 km. This paper describes the SondRad instrument in the PHOCUS payload, a radiometer comprising two frequency channels (183 GHz and 557 GHz) aimed at exploring the water vapour concentration distribution in connection with the appearance of noctilucent (night shining) clouds. The design of the radiometer system has been done in a collaboration between Omnisys Instruments AB and the Group for Advanced Receiver Development (GARD) at Chalmers University of Technology where Omnisys was responsible for the overall design, implementation, and verification of the radiometers and backend, whereas GARD was responsible for the radiometer optics and calibration systems. The SondRad instrument covers the water absorption lines at 183 GHz and 557 GHz. The 183 GHz channel is a side-looking radiometer, while the 557 GHz radiometer is placed along the rocket axis looking in the forward direction. Both channels employ sub-harmonically pumped Schottky mixers and Fast Fourier Transform Spectrometers (FFTS) backends with 67 kHz resolution. The radiometers include novel calibration systems specifically adjusted for use with each frequency channel. The 183 GHz channel employs a continuous wave CW pilot signal calibrating the entire receiving chain, while the intermediate frequency chain (the IF-chain) of the 557 GHz channel is calibrated by injecting a signal from a reference noise source through a directional coupler. The instrument collected complete spectra for both the 183 GHz and the 557 GHz with 300 Hz data rate for the 183 GHz channel and 10 Hz data rate for the 557 GHz channel for about 60 s reaching the apogee of the flight trajectory and 100 s after that. With lossless data compression using variable resolution over the spectrum, the data set was reduced to 2 x 12 MByte. The first results indicate that the instrument successfully performed measurements of the mesospheric water profile as planned. However, the temperature environment for the instruments showed more extreme behaviour than expected and accounted for. Consequently, the results of the calibration and the final data reduction will need careful treatment. Further, simulations through finite element method (FEM), modelling and direct measurements of the simulated thermal environment and its impact on the instrument performance are described, as well as suggestions for improvements in the design for future flights.
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| 24. |
- Nyström, Olle, 1979, et al.
(författare)
-
PHOCUS Radiometer Payload
- 2011
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Ingår i: Proceedings of the 22nd International Symposium on Space Terahertz Technology, Tucson, AZ, USA, April 26-28, 2011. ; , s. P-9
-
Konferensbidrag (refereegranskat)abstract
- PHOCUS – Particles, Hydrogen and Oxygen Chemistry in the Upper Summer Mesosphere is a Swedish sounding rocket experiment with the main goal of investigating the upper atmosphere in the altitude range 50-110 km. This paper describes the radiometer instruments (SondRad) in the PHOCUS payload, which are intended to explore the water vapour concentration in connection with the appearance of noctilucent (night shining) clouds. The design of the radiometer system has been done in collaboration between Omnisys Instruments AB and the Group for Advanced Receiver Development (GARD) at Chalmers University of Technology where Omnisys was responsible for the design, implementation, and verification of the radiometers and backend and GARD was responsible for the optics and calibration systems. The radiometers cover the water absorption lines at 183 GHz and 557 GHz with 67 kHz backend resolution. The 183 GHz channel is a side-looking radiometer while the 557 GHz radiometer is placed along the rocket axis looking in the forward direction. Both channels employ sub-harmonically pumped Schottky mixers and FFT spectrometer back-ends. The 183 GHz channel employs a CW-pilot signal calibrating the entire receiving chain while the IF-chain of the 557 GHz channel is calibrated by injecting a signal from a calibrated noise source through a directional coupler. The instrument will collect complete spectra for both the 183 and 557 GHz with 300 Hz rate for the 183 GHz channel and 10 Hz for the 557 GHz channel for about 60 seconds reaching the apogee of the flight trajectory and 100 seconds after that. With lossless data compression using variable resolution over the spectrum, the data set is reduced to 2 x 12 MByte.
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| 25. |
- Nyström, Olle, 1979
(författare)
-
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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