| 1. |
- Alef, Walter, et al.
(författare)
-
BRAND - The next generation receiver for VLBI
- 2018
-
Ingår i: Proceedings of Science. - Trieste, Italy : Sissa Medialab. - 1824-8039. ; 344
-
Konferensbidrag (refereegranskat)abstract
- The aim of the BRAND EVN project is to build a very wide receiver prototype for primary focus with a frequency range from 1.5 GHz to 15.5 GHz In addition we will investigate solutions for secondary focus telescopes. The project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 730562 [RadioNet]. We present the status of the project which was started on January 1st, 2017 and is progressing smoothly: Feed, LNA, filters, major digital components, and some of the firmware are available now. © Copyright owned by the author(s) under the terms of the Creative Commons.
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| 2. |
- Algaba Brazalez, Astrid, 1983, et al.
(författare)
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Design of F-Band Transition From Microstrip to Ridge Gap Waveguide Including Monte Carlo Assembly Tolerance Analysis
- 2016
-
Ingår i: IEEE Transactions on Microwave Theory and Techniques. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9480 .- 1557-9670. ; 64:4, s. 1245-1254
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the design and realization of a transition from a microstrip line to a ridge gap waveguide operating between 95 and 115 GHz. The study includes simulations, measurements, and a Monte Carlo analysis of the assembly tolerances. The purpose of this tolerance study is to identify the most critical misalignments that affect the circuit performance and to provide guidelines about the assembly tolerance requirements for the proposed transition design.
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| 3. |
- Atia Abdalmalak, Kerlos, et al.
(författare)
-
Ultrawideband Conical Log-Spiral Circularly Polarized Feed for Radio Astronomy
- 2020
-
Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 68:3, s. 1995-2007
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Tidskriftsartikel (refereegranskat)abstract
- In order to meet the requirements of the new generation of radio telescopes, we have developed a new topology called DYQSA, which stands for DYson Quad-Spiral Array. The design exhibits dual circular polarization contrary to dual linear polarization of state-of-the-art feeds. It covers the required ultrawideband (UWB) from 2 to 14 GHz with an almost constant and real input impedance which facilitates the design of the feeding structure and the low-noise amplifiers (LNAs). Different versions are investigated for enhancing feed performance, ensuring higher aperture efficiencies and mechanical stability. The simulation results of the reflector loaded by the proposed feed show an aperture efficiency of 65%±5% with a noise antenna temperature around 14 K and a system equivalent flux density (SEFD) of about 1300 Jy, both averaged over the required bandwidth at zenith. Measurements of the single-element and the four-element feeds are presented. Comparisons with other state-of-the-art feeds are shown in terms of total aperture efficiencies, design adaptability to different reflectors, calibration signal injection, and the required number of LNAs per feed, cost, and physical volume.
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| 4. |
- Belitsky, Victor, 1955, et al.
(författare)
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A new 3 mm band receiver for the Onsala 20 m antenna
- 2015
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 580
-
Tidskriftsartikel (refereegranskat)abstract
- A new receiver for the Onsala 20 m antenna with the possibility of being equipped with 3 mm and 4 mm bands has been built and the 3 mm channel has been commissioned during the Spring 2014. For single-dish operation, the receiver uses an innovative on-source/off-source optical switch. In combination with additional optical components and within the same optical layout, the switch provides two calibration loads (for the 3 mm and 4 mm channels), sideband rejection measurement, and tuning possibilities. The optical layout of the receiver employs all cold (4 K) offset elliptical mirrors for both channels, whereas the on-off switch employs flat mirrors only. The 3 mm channel employs a sideband separation (2SB) dual polarization receiver with orthomode transducer (OMT), 4-8 GHz intermediate frequency (IF), x? 2pol x? upper and lower sidebands (USB? +? LSB). The cryostat has four optical windows made of high density polyethylene (HDPE) with anti-reflection corrugations, two for the signal and two for each frequency band cold load. The cryostat uses a two-stage cryocooler produced by Sumitomo HI? RDK? 408D2 with anti-vibration suspension of the cold-head to minimize impact of the vibrations on the receiver stability. The local oscillator (LO) system is based on a Gunn oscillator with aphase lock loop (PLL) and four mechanical tuners for broadband operation, providing independently tunable LO power for each polarization. This paper provides a technical description of the receiver and its technology and could be useful for instrumentation engineers and observers using the Onsala 20 m telescope.
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| 5. |
- Billade, Bhushan, 1982, et al.
(författare)
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A Wide-band Feed System for SKA Band 1 Covering Frequencies From 350 - 1050 MHz
- 2016
-
Ingår i: 10th European Conference on Antennas and Propagation, EuCAP 2016; Davos; Switzerland; 10 April 2016 through 15 April 2016. - 2164-3342. - 9788890701863 ; , s. Art. no. 7481794-
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Konferensbidrag (refereegranskat)abstract
- We present the design of a wideband feed system for the Band 1 of the Square Kilometer Array (project). The Band 1 feed system uses a quad-ridged flared horn (QRFH) optimizedfor a offset Gregorian dual reflector dish to cover RF frequencies from 350 - 1050 MHz, and a cryogenic low noise amplifier (LNA). The feed horn is optimized to achieve best Aeff/Tsys over the entire band, by making trade-off between aperture efficiency and spill over noise contribution. The optimised feed horn shows above 70% efficiency over the entire 3:1 band, with return loss better than 10 dB. The cryostat following the feed has between 9 to 14 K noise, measured at the co-axial connector of the QRFH. The estimated on-sky sensitivity of the feed system is better than specified 4.2 m2/K averaged over the entire frequency band.
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| 6. |
- Carozzi, Tobia, 1966, et al.
(författare)
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Enhancing SKA Band 1 Polarimetry by Using Two Different Feed Rotations
- 2018
-
Ingår i: 2018 2nd URSI Atlantic Radio Science Meeting, AT-RASC 2018. - 9789082598735
-
Konferensbidrag (refereegranskat)abstract
- We investigate the possibility of enhancing the polarimetric performance of the Square Kilometre Array (SKA) telescope's band 1 by mounting the feeds with two different rotations relative the dish. One rotation aligns the two polarizations along the horizontal and vertical directions and the other rotation is 45 degrees to the horizontal, vertical directions. Taken together, this configuration amounts to introducing a simple and cheap type of polarization diversity. We find that such a configuration can improve polarimetry. This is important since the offset gregorian dish design employed for SKA1-mid tends to produce beam-shapes that are not rotationally symmetric, and thus polarimetry tends to vary azimuthally.
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| 7. |
- Connor, Liam, et al.
(författare)
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Galactic Radio Explorer: An All-sky Monitor for Bright Radio Bursts
- 2021
-
Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 133:1025
-
Tidskriftsartikel (refereegranskat)abstract
- We present the Galactic Radio Explorer (GReX), an all-sky monitor to probe the brightest bursts in the radio sky. Building on the success of STARE2, we will search for fast radio bursts emitted from Galactic magnetars as well as bursts from nearby galaxies. GReX will search down to similar to ten microseconds time resolution, allowing us to find new super giant radio pulses from Milky Way pulsars and study their broadband emission. The proposed instrument will employ ultra-wide band (0.7-2 GHz) feeds coupled to a high-performance (receiver temperature <10 K) low noise amplifier originally developed for the DSA-110 and DSA-2000 projects. In GReX Phase I (GReX-I), unit systems will be deployed at Owens Valley Radio Observatory and Big Smoky Valley, Nevada. Phase II will expand the array, placing feeds in India, Australia, and elsewhere in order to build up to continuous coverage of nearly 4 pi steradians and to increase our exposure to the Galactic plane. We model the local magnetar population to forecast for GReX, finding the improved sensitivity and increased exposure to the Galactic plane could lead to dozens of FRB-like bursts per year.
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| 8. |
- Dong, Bin, 1984, et al.
(författare)
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Design of an Asymmetrical Quadruple-ridge Flared Horn Feed: a Solution to Eliminate Polarization Discrepancy in the Offset Reflecting Systems
- 2018
-
Ingår i: IET Conference Publications. ; 2018:CP741
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Konferensbidrag (refereegranskat)abstract
- Quadruple-ridge Flared Horns (QRFHs) have been showing qualified performance as the feed antennas for the reflecting systems in the Square Kilometre Array (SKA). However, due to the offset optics of the SKA reflecting system, identical illuminations from dual polarizations of the feed would but result in different system performance. This difference would become more severe towards high frequencies and may cause the worse polarization unqualified for the desired specification. In this paper, an asymmetrical QRFH feed working over Band B (4.6–24 GHz) is proposed and optimized to tackle this problem.The asymmetrical Band-B feed is composed of two different and orthogonal pairs of both ridges and sidewall quad-pieces, so as to provide orthogonal polarizations but different illuminations. Simulated results show that, by this asymmetrical design different beamwidths and different combinations of sub-efficiencies can be provided for two polarizations, so as to eliminate the polarization discrepancy over most of the bandwidth. Benefitting from this elimination, both polarizations of the Band-B feed have now achieved the SKA specification in terms of aperture efficiency.
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| 9. |
- Dong, Bin, 1984, et al.
(författare)
-
Optimization and Realization of Quadruple-ridge Flared Horn with New Spline-defined Profiles as a High-efficiency Feed over 4.6–24 GHz
- 2019
-
Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 67:1, s. 585-590
-
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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| 10. |
- Flygare, Jonas, 1988, et al.
(författare)
-
Beam pattern measurement on offset Gregorian reflector mounted with a wideband room temperature receiver for the Square Kilometre Array
- 2018
-
Ingår i: 2018 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting (APSURSI2018). - 9781538671023 ; APSURSI 2018, s. 1759-1760
-
Konferensbidrag (refereegranskat)abstract
- We present measured on-dish beam patterns for a room temperature spline-profile quad-ridge flared horn (QRFH) feed designed for the Square Kilometre Array (SKA) Band 1 covering 350-1050 MHz. The feed and LNA package has been mounted on the offset Gregorian SKA precursor prototype telescope, Dish Verification Antenna 1 (DVA-1) located at the Dominion Radio Astrophysical Observatory (DRAO) near Penticton, British Columbia, Canada. Telescope beam pattern cuts are measured by sweeping over the sun and adding corrections for the solar disk size, elevation and aperture efficiency. Sensitivity calculated with measured receiver noise show good agreement with the predicted performance.
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| 11. |
- Flygare, Jonas, 1988, et al.
(författare)
-
Beyond-Decade Ultrawideband Quad-Ridge Flared Horn With Dielectric Load From 1 to 20 GHz
- 2023
-
Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 71:3, s. 2110-2125
-
Tidskriftsartikel (refereegranskat)abstract
- In this article, we present a novel dielectrically loaded quad-ridge flared horn (QRFH) as a reflector feed with beyond-decade ultrawideband performance. The dielectric is machined in a low-loss, space-grade polyimide specified with low outgassing for a vacuum environment. The feed covers 1–20 GHz bandwidth with a measured band-average input reflection of −13.6 and 41.5 dB isolation between two orthogonal polarized ports. Predicted performance in a paraboloidal reflector with a 60° half-subtended angle is 62% aperture efficiency average over the band. The ridges of the horn are designed with analytic-spline-hybrid 3-D profiles with thickness flaring outwards toward the feed aperture, improving low-frequency polarization properties. The QRFH was manufactured in four quarters for accurate ridge-to-ridge alignment and a reduced number of interfaces for good thermal properties in cryogenic applications. A prototype feed has been installed and tested with promising results in one of the 6 m offset Gregorian reflectors of the Allen Telescope Array (ATA) located at the Hat Creek Observatory, Hat Creek, CA, USA.
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| 12. |
- Flygare, Jonas, 1988, et al.
(författare)
-
BRAND: Ultra-Wideband Feed Development for the European VLBI Network - A Dielectrically Loaded Decade Bandwidth Quad-Ridge Flared Horn
- 2018
-
Ingår i: IET Conference Publications. - : Institution of Engineering and Technology. ; 2018:CP741
-
Konferensbidrag (refereegranskat)abstract
- We present the design of an ultra-wideband dielectrically loaded Quad-Ridge Flared Horn (QRFH) feed for the European Very Long Baseline Interferometry Network (EVN) developed under the RadioNet project BRoad-bAND (BRAND). The feed covers a frequency bandwidth ratio of 10:1 and has an average aperture efficiency of 50 percent simulated in primary focus setup on the Effelsberg telescope (f/D = 0.3). The feed is dual-polarized and has an input reflection better than −10 dB over the whole 1.5–15.5 GHz frequency band. We also introduce an Analytic-Spline-Hybrid (ASH) optimization scheme for the QRFH ridge and sidewall profiles.
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| 13. |
- Flygare, Jonas, 1988, et al.
(författare)
-
Design trade-offs in feed systems for ultra-wideband VLBI observations
- 2018
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Due to the advanced capability of today’s ultra-wideband feed systems and low-noise amplifiers, interesting upgrades for future VLBI receiver and tele- scope design should be considered. Multiple input pa- rameters need to be taken into account for optimal sensitivity and applications of the future astronomical and geodetic observational systems. In this paper we present an overview of some trade-offs for wideband systems between SEFD, bandwidth and telescope re- flector optics. We evaluate receiver bandwidths from 3.5:1 to 10.3:1 bandwidth within the frequency range 1.5-24 GHz in different configurations. Due to poten- tial RFI-pollution of the lower frequencies we present potential feed upgrades for the most common reflector geometries ofVGOS and EVN telescopes that mitigate this problem. The results of this work is relevant for fu- ture VLBI stations and telescope design in general. Keywords
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| 14. |
- Flygare, Jonas, 1988, et al.
(författare)
-
Dielectrically Loaded Quad-Ridge Flared Horn for Beamwidth Control Over Decade Bandwidth-Optimization, Manufacture, and Measurement
- 2020
-
Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 68:1, s. 207-216
-
Tidskriftsartikel (refereegranskat)abstract
- We present the design, manufacture, and measured performance of a dielectrically loaded quad-ridge flared horn (QRFH) feed for decade bandwidth radio astronomy application. The introduction of the dielectric load improves the QRFH beamwidth control in H-plane at the mid and upper frequency range. Consequently on the reflector, illumination efficiency, phase efficiency, and the intrinsic cross-polarization ratio (IXR) have been improved. The dielectric load is made from homogeneous low-loss polytetrafluoroethylene and has a low profile with a cylinder shape for simple installation at the center of the QRFH. The dielectrically loaded QRFH presented here covers 1.5-15.5 GHz with a calculated average aperture efficiency above 50% on a f/D = 0.3 prime-focus reflector. We present a calculation of system noise temperature and sensitivity for the QRFH on a 100 m prime-focus reflector. Measured beam patterns of the QRFH are in good agreement with the simulations over the full frequency band. The input reflection coefficient was predicted to be below -10 dB across the bandwidth. We present a tolerance analysis that explains why the measured one deviates.
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| 15. |
- Flygare, Jonas, 1988
(författare)
-
Dielectrically Loaded Quad-ridge Flared Horns for Ultra Wideband Reflector Feed Applications in Radio Astronomy
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Reflector-based radio telescopes are used as tools for observations in both radio astronomy and space geodesy. To observe the weak sources in space, highly sensitive receivers, fronted by optimized reflector feeds, are therefore needed. Wideband and ultra-wideband (UWB) systems enable large continuous frequency bandwidth and reduce the number of receivers that are needed to cover the radio spectrum. Therefore, they are attractive for existing and next generation of reflector arrays such as the Square Kilometre Array (SKA), Allen Telescope Array (ATA), Deep Synoptic Array (DSA), and the Next Generation Very Large Array (ngVLA). To achieve sensitive wideband and UWB performance with reflector feeds, a near-constant beamwidth and good impedance match are required over large frequency bands. The quad-ridge flared horn (QRFH) is a robust and compact UWB feed technology for this purpose, and is easily designed with single-ended excitation for 50-Ohm ports. The QRFH is dual-linear polarized and can typically achieve good performance up to 6:1 bandwidth with high band-average aperture efficiency and good impedance match. A drawback in existing state-of-the-art QRFH designs, is that they suffer from gradually narrowing beamwidth and increasing cross-polarization in the upper part of the frequency band. This is especially challenging for QRFHs that are designed to illuminate deep reflector geometries. The narrowing beamwidth leads to reduced aperture efficiency, and therefore also reduced sensitivity. To meet the demand for high sensitivity observations over large bandwidths, these challenges need to be addressed. This thesis introduces and investigates low-loss, dielectric loading of the QRFH design to achieve ultra-wideband performance that reaches beyond decade bandwidth exemplified with 20:1 bandwidth in one single QRFH. The dielectric load is homogeneous, with a small and non-intrusive footprint and improves the beamwidth performance over the frequency band, while keeping the complexity low and the QRFH footprint compact. Keeping the QRFH robustness and compact footprint is favorable for practical receiver installation in real-world applications for radio observations. Three quad-ridge designs with dielectric loading are investigated, both for room temperature and cryogenic applications, and are shown to be highly suitable for wideband operation in existing and future reflector arrays.
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| 16. |
- Flygare, Jonas, 1988, et al.
(författare)
-
Integrated calibration noise coupler for room temperature SKA band 1 feed system
- 2017
-
Ingår i: Proceedings of 2017 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting, APSURSI 2017, San Diego, CA, USA, 9-14 July 2017. - 1947-1491. ; 2017, s. 777-778
-
Konferensbidrag (refereegranskat)abstract
- This paper presents design of a novel coupler for the injection of calibration signal into the RF path of the SKA Band 1 quad-ridged flared horn, covering frequencies from 350–1050 MHz. The coupler is integrated in the feed horn and provides a coupling factor of −35 dB. The calibration signal is injected before the first amplification stage, without any degradation in the noise performance of the room temperature system.
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| 17. |
- Flygare, Jonas, 1988, et al.
(författare)
-
Sensitivity and Antenna Noise Temperature Analysis of the Feed System for the Onsala Twin Telescopes
- 2017
-
Ingår i: Proceedings of the 23rd European Very Long Baseline Interferometry Group for Geodesy and Astrometry Working Meeting, EVGA2017, Gothenburg, Sweden, 15-19 May 2017. - 9789188041104 ; , s. 10-14
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The demand for higher precision measurements in Very Long Baseline Interferometry (VLBI) continues to grow, which drives the technical development of next generation international VLBI stations called the VLBI Global Observing System (VGOS). The VGOS design includes the idea of twin telescopes, i.e. two identical telescopes that will be used for continuous observations to study geodynamical processes. Such a twin telescope system has recently been installed at the Onsala Space Observatory, Sweden. The Onsala twin telescopes (OTT) are 13.2 m diameter, dual-reflector systems with a ring-focus sub-reflector. In this paper we present the estimated performance, focusing on the achievable system equivalent flux density (SEFD), sky noise modeling, and antenna noise temperature. We evaluate the system for two different cryogenic wideband quad-ridge flared horn (QRFH) feed setups operating over 3-18 GHz and 4.6-24 GHz. Analysis based on measured feed data shows a low antenna noise temperature and that SEFD of 1000 Jy can be achieved for the system. The result from Y-factor test shows TREC = 10 K over most of the frequency band.
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| 18. |
- Flygare, Jonas, 1988, et al.
(författare)
-
Sensitivity simulation and measurement of the SKA Band 1 wideband feed package on MeerKAT
- 2019
-
Ingår i: 13th European Conference on Antennas and Propagation, EuCAP 2019. ; EuCAP 2019
-
Konferensbidrag (refereegranskat)abstract
- Advances in wideband feed technology for radio telescopes enable high sensitivity observations over large bandwidths. The wideband quad-ridge flared horn (QRFH) feed package for Band 1 of the Square Kilometre Array (SKA) was optimized for high sensitivity. The 3:1 feed package covers 350-1050 MHz and is a complete room temperature system with low-noise amplifiers integrated inside the ridges of the horn. The QRFH is dual-linear polarized and designed with spline-defined profiles for the horn and ridge shape. Measured feed s-parameters show input reflection less than -11 dB across the band with good port isolation. In this paper we present the first measured sensitivity levels of the Band 1 feed package, which was tested on the SKA precursor reflector MeerKAT. We also present measured aperture efficiency and intrinsic cross-polarization (IXR). The measured results show good agreement with simulations.
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| 19. |
- Flygare, Jonas, 1988, et al.
(författare)
-
Strategy and Overview for Development of Beyond-Decade-Bandwidth Quad-ridge Flared Horns for Radio Astronomy
- 2021
-
Ingår i: 15th European Conference on Antennas and Propagation, EuCAP 2021.
-
Konferensbidrag (refereegranskat)abstract
- This paper considers the potential of the dielectrically loaded Quad-ridge Flared Horn (QRFH) feed to provide continuous beyond-decade bandwidth in reflector telescopes for radio astronomy. An overview of the beam pattern evolution over frequency in a recent ultra-wideband feed designed for 1.5–15.5 GHz is presented.
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| 20. |
- Flygare, Jonas, 1988
(författare)
-
Ultra-wideband feed design and characterization for next generation radio telescopes
- 2018
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Radio telescopes are used as tools for observations in both radio astronomy and geodesy. To observe the weak sources in space, highly sensitive receivers headed by optimized reflector feeds are needed. Wideband and ultra-wideband (UWB) receiver systems enable large continuous frequency bandwidth and reduce the number of receivers that are needed. Therefore, they are attractive for the next generation of large reflector arrays such as the Square Kilometre Array (SKA) and the Next Generation Very Large Array (ngVLA). To achieve highly sensitive wideband and UWB performance with reflector feeds, a near-constant beamwidth and good impedance match are required over large frequency bands. The quad-ridge flared horn (QRFH) is a robust and popular UWB feed technology for this purpose. Typically, the QRFH achieve good performance up to 6:1 bandwidth and are designed for high aperture efficiency. However, due to the very small noise contributions of today's low-noise amplifiers (LNA), it is becoming more relevant to design specifically for high sensitivity. A drawback in existing state-of-the-art QRFH designs, is that they suffer from narrowing beamwidth as the frequency increases over the bandwidth. To meet the demand for high sensitivity observations over large bandwidths, these challenges need to be addressed. In this thesis, the spline-defined QRFH design for the room temperature SKA Band 1 feed package over 350-1050 MHz is presented. The QRFH spline-profile is optimized for high sensitivity over the 3:1 bandwidth for the SKA reflector dish. The thesis also introduces a low-profiled dielectric load at the center of a QRFH design for 10:1 bandwidth for the BRAND project. The dielectric load improves the beamwidth performance over the 1.5-15.5GHz frequency band, while keeping the complexity of the QRFH concept low. Both of the approaches that are introduced here are applicable for any future QRFH design, and are therefore relevant for the community in the hunt for high sensitivity observations.
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| 21. |
- Flygare, Jonas, 1988, et al.
(författare)
-
Ultra-wideband feed systems for the EVN and SKA - evaluated for VGOS
- 2018
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The design of the Square Kilometre Array (SKA) project for radio astronomy is now materializing at a rapid speed; the EU Horizon 2020 RadioNet project BRoad-bAND (BRAND) has the ambition to deliver a decade bandwidth receiver for EVN. The ultra-wideband quad-ridge flared horn (QRFH) feed systems developed for these projects show good performance within the geodetic VLBI Global Observing System (VGOS) frame due to the overlapping frequency bands and reflector geometries. We estimate, through simulation, system equivalent flux density (SEFD) of the two feed systems in the VGOS reflector and compare the it to the existing system installed on one of the 13.2 m diameter reflectors of the Onsala twin telescope (OTT). The two frequency bands analyzed cover 1.5−15.5 GHz and 4.6−24 GHz. Both systems show SEFD better than 1000 Jy over large parts of resp. frequency band - comparable to the 3−18 GHz feed systems. For the SKA QRFH over 4.6−24 GHz, the water vapor absorption line at 22 GHz is within the operational band, therefore we study the application of water-vapor radiometry in line-of-sight of the telescope.
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| 22. |
- Flygare, Jonas, 1988, et al.
(författare)
-
Wideband single pixel feed system over 4.6-24 GHz for the Square Kilometre Array
- 2019
-
Ingår i: Proceedings of the 2019 21st International Conference on Electromagnetics in Advanced Applications, ICEAA 2019. ; , s. 630-635
-
Konferensbidrag (refereegranskat)abstract
- We present the Band B feed system over 4.6-24 GHz designed for the Square Kilometre Array (SKA) reflector for radio astronomy applications. The feed is a Quad-ridge Flared Horn (QRFH) with a customized shape based on spline-defined profiles to achieve improved wideband performance. The feed system shows high aperture efficiency and sensitivity on the SKA reflector in predictions based on measured feed beam patterns. We present the feed design overview, cryogenic dewar concept and measurement of receiver noise (10-20 K) with wideband low-noise amplifiers, and full system simulation of the performance.
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| 23. |
- Forkman, Peter, 1959, et al.
(författare)
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Water vapour radiometry in geodetic very long baseline interferometry telescopes: assessed through simulations
- 2021
-
Ingår i: Journal of Geodesy. - : Springer Science and Business Media LLC. - 0949-7714 .- 1432-1394. ; 95:11
-
Tidskriftsartikel (refereegranskat)abstract
- The accuracy of geodetic Very Long Baseline Interferometry (VLBI) is affected by water vapour in the atmosphere in terms of variations in the signal propagation delay at the different stations. This “wet” delay may be estimated directly from the VLBI data, as well as from independent instruments, such as collocated microwave radiometers. Rather than having stand-alone microwave radiometers we have, through simulations, evaluated the possibility to use radiometric data from the VLBI receiver in the VGOS telescopes at the Onsala Space Observatory. The advantage is that the emission from water vapour, as sensed by the radiometer, originates from the same atmospheric volume that delays the VLBI signal from the extra-galactic object. We use simulations of the sky brightness temperature and the wet delay together with an assumption of a root-mean-square (rms) noise of the receiver of 1 K, and observations evenly spread between elevation angles of 10∘–90∘. This results in an rms error of the estimated equivalent zenith wet delay of the order of 3 mm for a one frequency algorithm, used under cloud free conditions, and 4 mm for a two frequency algorithm, used during conditions with liquid water clouds. The results exclude rainy conditions when the method does not work. These errors are reduced by a factor of 3 if the receiver error is 0.1 K meaning that the receivers’ measurements of the sky brightness temperature is the main error source. We study the impact of ground-noise pickup by using a model of an existing wideband feed. Taking the algorithm uncertainty and the ground noise pickup into account we conclude that the method presented will be useful as an independent estimate of the wet delay to assess the quality of the wet delays and linear horizontal gradients estimated from the VLBI data themselves.
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| 24. |
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| 25. |
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| 26. |
- Pellegrini, Alice, et al.
(författare)
-
MID-Radio Telescope, Single Pixel Feed Packages for the Square Kilometer Array: An Overview
- 2021
-
Ingår i: IEEE Journal of Microwaves. - 2692-8388. ; 1:1, s. 428-437
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Tidskriftsartikel (refereegranskat)abstract
- The Square Kilometre Array (SKA) project is an international effort to build the world's largest radio telescope, enabling science with unprecedented detail and survey speed.The project spans over a decade and is now at a mature stage, ready to enter the construction and integration phase. In the fully deployed state, the MID-Telescope consists of a 150-km diameter array of offset Gregorian antennas installed in the radio quiet zone of the Karoo desert (South Africa). Each antenna is equipped with three feed packages, that are precision positioned in the sub-reflector focus by a feed indexer platform. The total observational bandwidth (0.35-15.4GHz) is segmented into seven bands. Band 1 (0.35 – 1.05 GHz) and Band 2 (0.95 – 1.76 GHz) are implemented as individual feed packages. The remaining five bands (Bands 3, 4, 5a, 5b, and 6) are combined in a single feed package. Initially only Band 5a (4.6 – 8.5 GHz) and Band 5b (8.3 – 15.4 GHz) will be installed. This paper provides an overview of recent progress on design, test and integration of each feed package as well as project and science goals, timeline and path to construction.
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| 27. |
- Svanelöv, Eric, 1988-, et al.
(författare)
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Funktionshinderidrott ett tveeggat svärd - men de positiva upplevelserna väger över
- 2020
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Ingår i: Idrottsforskning.se. - Stockholm : Centrum för Idrottsforskning. - 2002-3944. ; :8 Aug
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Funktionshinderidrotten är ett tveeggat svärd - den kan både stärka deltagarnas identiteter och sociala relationer, men även upplevas vara exkluderande och marginaliserande från annan idrott. Men i slutändan väger det positiva över, menar deltagarna själva.
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| 28. |
- Tuccari, Gino, et al.
(författare)
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BRAND: A Very Wide-band Receiver for the EVN
- 2017
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Ingår i: Proceedings of the 23rd European Very Long Baseline Interferometry Group for Geodesy and Astrometry Working Meeting, EVGA2017, Gothenburg, Sweden, 15-19 May 2017. - 9789188041104 ; , s. 81-83
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- BRAND stands for BRoad bAND EVN, a project to build a prototype primary focus receiver with the very wide frequency range from 1.5 GHz to 15.5 GHz, to investigate secondary focus solutions, and to make a survey of the EVN telescopes in order to set the stage for equipping all EVN stations with such a receiver as soon as possible. The project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 730562 and is a Joint Research Activity (JRA) in the RadioNet programme. We present the motivation, aims, scope and status of the project which was started on January 1st, 2017.
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| 29. |
- Walker, G. W., et al.
(författare)
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Optical design and verification of the 4mm receiver for the 20m telescope at Onsala Space Observatory
- 2018
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 10015
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Konferensbidrag (refereegranskat)abstract
- The work of this research is the design, analysis and verification of the optical performance of a 4 mm receiver channel for the 20 m telescope at Onsala Space Observatory, Onsala, Sweden. The 4 mm (75 GHz) receiver is a newly proposed channel designed to be installed parallel to the existing 3 mm (100 GHz) channel targeting new science at that longer wavelength. Gaussian beam mode analysis is used to produce the fundamental optical design of the system. The design is then analysed more accurately with the physical optics approximation. We report on the comparison of simulation and measurement and verification of the system design.
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| 30. |
- Weinreb, Sander, et al.
(författare)
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Cryogenic 1.2 to 116 GHz Receiver for Large Arrays
- 2018
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Ingår i: IET Conference Publications. - : Institution of Engineering and Technology. ; 2018:CP741
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Konferensbidrag (refereegranskat)abstract
- Current and future large arrays for radio astronomy are compared and the Next Generation Very Large Array, ngVLA, is introduced. Receiver requirements are described and a 4-feed system covering 1.2 to 116 GHz, in a single vacuum cryogenic enclosure is presented followed by description of the reflector optics, the wide-band feeds, and the expected system performance
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| 31. |
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