| 1. |
- Meledin, Denis, 1974, et al.
(författare)
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Balanced Waveguide HEB Mixer for APEX 1.3 THz Receiver
- 2006
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Ingår i: Proceedings of 16th International Symposium on Space Terahertz Technology, Chalmers University of Technology, Gothenburg, Sweden, May 2-4, 2005. - 1652-0769. ; , s. 214-216
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 2. |
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| 3. |
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| 4. |
- Alef, Walter, et al.
(författare)
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BRAND - The next generation receiver for VLBI
- 2018
-
Ingår i: Proceedings of Science. - Trieste, Italy : Sissa Medialab. - 1824-8039. ; 344
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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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| 5. |
- Atia Abdalmalak, Kerlos, et al.
(författare)
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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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| 6. |
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| 7. |
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| 8. |
- 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
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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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| 9. |
- Belitsky, Victor, 1955, et al.
(författare)
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Heterodyne Single-Pixel Facility Instrumentation for APEX Telescope
- 2006
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Ingår i: in "Millimeter and Submillimeter Detectors for Astronomy III", eds. J. Zmuidzinas, W.S. Holland, S. Withington, W.D. Duncan, Proceedings of SPIE. ; 6275, s. 15-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 10. |
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| 11. |
- Belitsky, Victor, 1955, et al.
(författare)
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Superconducting microstrip line models at millimeter and sub-millimeter waves and their comparison
- 2003
-
Ingår i: Proceedings of the 14th International Symposium on Space and Terahertz technology. ; , s. 456-475
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Konferensbidrag (refereegranskat)abstract
- Performance of superconductor — insulator - superconductor (SIS) tunnel junction mixers andtheir instantaneous input RF bandwidth are mostly depending on the integrated tunin g circuit used to resonate out SIS junction capacitance; Nb-based SIS mixers operate in the frequency range of about 80 - 1000 GHz and typically use microstrip-based integrated tuning circuitries.One of the major challenges in designing the tuning circuitry for SIS mixers is accuracy of models for superconducting microstrip line (SML). Modeling gives the only tool to solve the problem of designing SML-based circuits because for such high frequencies no direct measurements of a superconducting transmission line can be made with required high accuracy.However, creating an accurate model for such a superconducting transmission line is a challengeby itself. In the SML, produced usually by thin-film technology, the magnetic field penetrationdepth is comparable with the thicknesses of the dielectric and superconductors comprising theline. As a result the electromagnetic wave is propagated not only in the dielectric media but alsoinside the superconducting strip and ground electrodes constituting the SML. This createsdramatic changes in the transmission line behavior that should be carefully accounted byincluding the superconducting material properties into the modeling. Nb superconductor, as themost commonly exploited material, was used in this study for modeling of the superconductingmicrostrip though the same approach would work for any different BCS superconductingmaterial. The purpose of this paper is to introduce a new model for SML and compare it withpreviously suggested models and results of SML numerical simulation.
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| 12. |
- 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
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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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| 13. |
- 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
-
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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| 14. |
- Dong, Bin, 1984, et al.
(författare)
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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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| 15. |
- Elgered, Gunnar, 1955, et al.
(författare)
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The Onsala Twin Telescopes Project
- 2017
-
Ingår i: The 23rd Working Meeting of the European VLBI Group for Geodesy and Astrometry (EVGA), Gothenburg, May 14–18, 2017.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Onsala Space Observatory is the European site in the International VLBI Service for Geodesy and Astrometry (IVS) that has the longest history in VLBI. First geodetic VLBI measurements were performed already in 1968 with the 25 m radio telescope. Onsala is today one of the sites with thelongest time series in the IVS data base. The observatory is one of the unique fundamental space geodetic sites that have a direct access to the coast line and co-locate VLBI, GNSS, gravimetry, and sea-level monitoring. Onsala is thus an important co-location site for the GlobalGeodetic Observing System (GGOS). Being well aware of the VGOS standard it was clear around 2010 that Onsala was in need for a telescope with significantly faster slew rates than the existing radome-enclosed 20 m telescope.
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| 16. |
- Elgered, Gunnar, 1955, et al.
(författare)
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The Onsala Twin Telescopes: the Status at the Time for the Inauguration
- 2017
-
Ingår i: Proceedings of the 23rd European VLBI Group for Geodesy and Astrometry Working Meeting. - 9789188041098 ; , s. 136-139
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We summarise the activities related to the Onsala Twin Telescopes (OTT), from the time when the decision was taken to fund the proposal, to the inauguration on 18 May 2017.
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| 17. |
- Emrich, Anders, 1962, et al.
(författare)
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Wideband Receivers for VLBI2010 Applications
- 2013
-
Ingår i: Progress in Electromagnetics Research Symposium, PIERS 2013, Stockholm, Sweden, August 12-15, 2013.
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Konferensbidrag (refereegranskat)
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| 18. |
- Fan, Jin, et al.
(författare)
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Design of Octave-bandwidth Phased Array Feed for Large Radio Telescope
- 2019
-
Ingår i: 13th European Conference on Antennas and Propagation, EuCAP 2019.
-
Konferensbidrag (refereegranskat)abstract
- This paper presents design scenarios of Octave-bandwidth Phase Array Feed (PAF) based on a novel wideband dual polarized tightly-fed Bowtie antenna element. The PAF is optimized for the 4 - 8GHz band aiming to possible later integration in the SKA pathfinder PHAROS2. The proposed design can be a good candidate of PAF for the Five hundred meter Aperture Spherical Telescope (FAST) and Qi Tai Telescope (QTT) as well as other large radio telescopes.
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| 19. |
- Flygare, Jonas, 1988, et al.
(författare)
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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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| 20. |
- Flygare, Jonas, 1988, et al.
(författare)
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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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| 21. |
- 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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| 22. |
- Flygare, Jonas, 1988, et al.
(författare)
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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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| 23. |
- 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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| 24. |
- 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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| 25. |
- 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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| 26. |
- 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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| 27. |
- 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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| 28. |
- Geralt bij de Vaate, J., et al.
(författare)
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Wide bandwidth integrated 1-4 GHz feed development for VLBI and SKA
- 2012
-
Ingår i: Proceedings of Science. - 1824-8039. ; 2012-October
-
Konferensbidrag (refereegranskat)abstract
- Wide-band single pixel feeds such as the wide-band Eleven feed developed in Europe through Onsala Space Observatory/Chalmers are rapidly increasing in maturity. Compared to the traditional octave bandwidth feeds, wide bandwidth feeds, such as the Eleven feed, will create the possibility of significantly larger instantaneous frequency coverage observations with existing radio telescopes, such as those used in the VLBI networks, and for future radio telescopes, such as the Square Kilometre Array. This Project is supported by RadioNet3, Developments In VLBI Astronomy (DIVA).
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| 29. |
- Güsten, R., et al.
(författare)
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APEX - The Atacama Pathfinder Experiment
- 2006
-
Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 6267 I
-
Konferensbidrag (refereegranskat)abstract
- APEX, the Atacama Pathfinder Experiment, has been successfully commissioned and is in operation now. This novel submillimeter telescope is located at 5107 m altitude on Llano de Chajnantor in the Chilean High Andes, on what is considered one of the world's outstanding sites for submillimeter astronomy. The primary reflector with 12 m diameter has been carefully adjusted by means of holography. Its surface smoothness of 17-18 μm makes APEX suitable for observations up to 200 μm, through all atmospheric submm windows accessible from the ground.
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| 30. |
- Haas, Rüdiger, 1966, et al.
(författare)
-
Onsala Space Observatory – IVS Technology Development Center
- 2009
-
Ingår i: In: International VLBI Service for Geodesy and Astrometry 2008 Annual Report, edited by D. Behrend and K. Baver. ; NASA/TP-2009-214183, 2009, s. 329-332
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 31. |
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| 32. |
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| 33. |
- Haas, Rüdiger, 1966, et al.
(författare)
-
Status of the Onsala Twin Telescopes – One Year After the Inauguration
- 2019
-
Ingår i: IVS 2018 General Meeting Proceedings "Global Geodesy and the Role of VGOS – Fundamental to Sustainable Development". ; NASA/CP-2019-219039, s. 17-19
-
Konferensbidrag (refereegranskat)abstract
- We briefly describe the status of the Onsala twin telescopes and the experience gained since the official inauguration in May 2017.
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| 34. |
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| 35. |
- Ivashina, Marianna, 1975, et al.
(författare)
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Design of Wideband Quadruple-Ridged Flared Horn Feeds for Future Radio Telescopes
- 2014
-
Ingår i: Swedish Microwave Days March 11-12, 2014, Gothenburg, Sweden.
-
Konferensbidrag (refereegranskat)abstract
- Balanced excitations are required to achieve ultra wideband performance with the novel reflector antenna feeds consisting of pair(s) of interleaved spiral, log-periodical or other travelling-wave structures, which are currently being developed for radio astronomic instruments [1]–[3]. This excitation is commonly realized by using a balun interfacing the balanced antenna to single-ended amplifiers. However, practical designs of such passive networks are often bulky and lead to power dissipation losses. Power dissipation reduces the antenna radiation efficiency and increases the system thermal noise temperature. Another limiting factor is that the ultra wideband balun design restricts the reference impedance for the optimum noise matching between the antennas and low-noise amplifiers (LNAs). To obviate these disadvantages, differential low-noise amplifiers (dLNA), which can be directly integrated at the antenna terminals, represent an interesting alternative solution.
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| 36. |
- Ivashina, Marianna, 1975, et al.
(författare)
-
System noise performance of ultra-wideband feeds for future radio telescopes: Conical-Sinuous Antenna and Eleven Antenna
- 2014
-
Ingår i: 2014 31th URSI General Assembly and Scientific Symposium, URSI GASS 2014, Beijing, China, 16-23 August 2014. - 9781467352253 ; , s. Art. no. 6930063-
-
Konferensbidrag (refereegranskat)abstract
- Next generation radio telescopes can greatly benefit from reflector antenna feeds that demonstrate very wide frequency bandwidth and can potentially realize low noise performance of the receivers. In this paper, we provide an overview of the current developments at the national radio observatories in Sweden and USA that make use of novel multi-port antenna feeds, such as the Sinuous Antenna and Eleven Antenna. The focus of this overview is on the system performance, when using this technology at high or very low frequencies, i.e. when the feed-receiver system is fully or partially (cryogenically) cooled.
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| 37. |
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| 38. |
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| 39. |
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| 40. |
- Klein, Benjamin, 1981, et al.
(författare)
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Development of a detailed system model of the Eleven feed receiver using the CAESAR software
- 2012
-
Ingår i: 6th European Conference on Antennas and Propagation, EuCAP 2012; Prague; Czech Republic; 26 March 2012 through 30 March 2012. - 9781457709180 ; , s. 3416-3420
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Konferensbidrag (refereegranskat)abstract
- A mathematically general method is presented for exporting the far-field patterns, radiation efficiency and impedance data, for multi-port antennas, from EM solvers to the microwave circuit simulator of the CAESAR software in order to perform the analysis of a multi-port antenna-receiver system. This hybrid modelling approach offers a few important advantages over the early developed modelling methods and standard simulation tools; including the capability to predict the correlated noise contributions due to both internal and external noise sources, while exploiting the translation/rotation symmetry of the antenna structure to reduce computation time. This approach is validated using folded dipole antennas and applied to model a more complex antenna-receiver system the Eleven antenna feed operating from 2 to 12 GHz which consists of four log-periodic dipole arrays co-integrated with LNAs, a balun and hybrid combining network. The Eleven feed receiver model is verified by comparing the simulation results with the measurements performed with a practical system.
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| 41. |
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| 42. |
- Lapkin, Igor, 1963, et al.
(författare)
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Dual Band MM-Wave Receiver for Onsala 20 m Antenna
- 2014
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Ingår i: Proceedings of the TWENTY-FIFTH INTERNATIONAL SYMPOSIUM ON SPACE TERAHERTZ TECHNOLOGY, April 27-30, 2014, Moscow, Russia. ; , s. 132-
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Konferensbidrag (refereegranskat)abstract
- We present the design and the first light results for the new dual band receiver (4 mm and 3 mm bands) for Onsala Observatory 20 m antenna. For single dish operation, the receiver uses innovative on-source/off-source optical switch. Within the same optical layout, the switch, in combination with additional optical components, provides 2 calibration loads and sideband measurements possibilities. The optics layout of the receiver uses offset elliptical cold mirrors for both channels whereas the on-off switch employs flat mirrors only. The 3 mm channel employs 2SB dual polarization receiver with OMT, 4-8 GHz IF, x 2pol x (USB+LSB). The cryostat has 4 optical widows made of HDPE with anti-reflection corrugations, two for the signal and two for each frequency band cold load. The cryostat employs a two stage cryocooler RDK 408D2 and uses anti-vibration suspension of the cold-head to minimize impact of the vibrations on the receiver stability. The LO system is based on Gunn oscillator with PLL and two mechanical tuners for broadband operation, providing independently tunable LO power for each polarization. At the conference, we will present details on the receiver optics, cryostat design and the result of the first on-sky observations.
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| 43. |
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| 44. |
- Meledin, Denis, 1974, et al.
(författare)
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APEX Band T2: A 1.25 – 1.39 THz Waveguide Balanced HEB Receiver
- 2008
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Ingår i: Proceedings of The 19th International Symposium on Space Terahertz Technology, Groningen, 28-30 April, 2008, ed. W. Wild, Space Research Organization of the Netherlands (SRON). ; part I, s. 162-166
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Konferensbidrag (refereegranskat)abstract
- A waveguide 1.25 - 1.39 THz Hot Electron Bolometer (HEB) balanced receiver was successfully developed, characterized and installed at the Atacama Pathfinder EXperiment (APEX) telescope. The receiver employs a quadrature balanced scheme using a waveguide 90-degree 3 dB RF hybrid, HEB mixers and a 180-degree IF hybrid. The HEB mixers are based on ultrathin NbN film deposited on crystalline quartz with a MgO buffer layer. Integrated into the multi-channel APEX facility receiver (SHeFI), the results presented here demonstrate exceptional performance; a receiver noise temperature of 1000 K measured at the telescope at the center of the receiver IF band 2-4 GHz, and at an LO frequency of 1294 GHz. Stability of the receiver is in line with the SIS mixer bands of the SHeFI, and gives a spectroscopic Allan time of more than 200 s at 1382 GHz with a noise bandwidth of 1 MHz.
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| 45. |
- Meledin, Denis, 1974, et al.
(författare)
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Waveguide Components Development for APEX 1.32 THz Receiver
- 2004
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Ingår i: in "Proceedings of 5th Workshop on MEMS for Millimeterwave Communication MEMSWAVE", 30 June-2 July, Uppsala, Sweden. ; , s. I1-I4
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 46. |
- Navarrini, A., et al.
(författare)
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Design of PHAROS2 Phased Array Feed
- 2018
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Ingår i: 2018 2nd URSI Atlantic Radio Science Meeting, AT-RASC 2018.
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Konferensbidrag (refereegranskat)abstract
- We describe the design and architecture of PHAROS2, a cryogenically cooled 4-8 GHz Phased Array Feed (PAF) demonstrator with digital beamformer for radio astronomy application. The instrument will be capable of synthesizing four independent single-polarization beams by combining 24 active elements of an array of Vivaldi antennas. PHAROS2, the upgrade of PHAROS (PHased Arrays for Reflector Observing Systems), features: a) commercial cryogenic LNAs with state-of-the-art performance, b) a 'Warm Section' for signal filtering, conditioning and single downconversion to select a≈275 MHz: Intermediate Frequency (IF) bandwidth within the 4-8 GHz Radio Frequency (RF) band, c) an IF signal transportation by analog WDM (Wavelength Division Mutiplexing) fiber-optic link, and d) a FPGA-based Italian Tile Processing Module (iTPM) digital backend. PHAROS2 will be mounted at the primary focus of the 76-m diameter Lovell radio telescope (Jodrell Bank Observatory, UK) for technical and scientific validation.
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| 47. |
- Nyström, Olle, 1979, et al.
(författare)
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A Vector Beam Measurement System for 211-275 GHz
- 2006
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Ingår i: Proceedings 17th International Symposium on Space Terahertz Technology, Paris, FRANCE.. ; , s. P2-28
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Konferensbidrag (refereegranskat)abstract
- We propose a novel design for a vector measurement system for the characterization of mm-wave receiver optics alignment across the 211-275 GHz band. Previous published work on vector mm and submm beam measurements employs phase-locked loops (PLLs) with Gunn-oscillators and/or multiple frequency sources, [1], [2]. We are developing a measurement set-up without any PLLs and employ the combination of a single frequency source, comb-generator and direct multiplication LO unit. The design takes advantage of different harmonics used to generate the RF and LO signals and to create the desired IF. Importantly, at the same time it allows obtaining a perfect phase-coherence and initial phase-noise cancellation.The signal source is a vector network analyzer (VNA). In the suggested scheme the VNA generates a signal, fsource, which is fed into a comb-generator that generates number of frequencies ∆fsource apart. When fsource is low, this results in a large number of closely spaced, phase-coherent frequencies. Since any selection among the generated frequencies is phase-coherent, any two of them can be used to produce phase-coherent RF and LO signals by filtering and multiplication. As a test source we use a harmonic mixer mounted on a xyz-scanner. Its absolute position with respect to the receiver optics is predefined by means of triangulation system comprising lasers and position sensitive detectors. The IF from the SIS mixer is down-converted using suitable reference from the comb generator to produce an IF equal to fsource. This signal is fed into Port 2 of the VNA and amplitude and phase are measured. The advantage of using comb generator is to have closely spaced frequencies to choose from and therefore ease the production of the desired IF-frequency and obtaining initial-phase-noise cancellation. Most of the phase-noise is cancelled in the down-conversion in the SIS-mixer and the remaining is cancelled in the second down-conversion before the measurements in the VNA. The cancellation of the remaining phase-noise present at IF is obtained by selecting also the LO, for the second down-conversion, from the harmonics generated by the comb-generator.We also propose to use the same measurement set-up for the frequency bands 275-370 GHz and 385-500 GHz. We believe that our system design has the potential to cover all three bands by only replacing two filters and the LO multiplication unit. Scalar beam measurements up to 320 GHz have already demonstrated a dynamic range of about 20 dB with the harmonic mixer as the RF transmitting source [3]. We expect that vector measurements provide even greater dynamic range, indicating that we can push the frequency even higher with this harmonic mixer as the RF comb source. At the moment we are in the assembly phase of the system design and intend to present results from measurements of the Band 1 of the Facility receiver for Atacama Pathfinder EXperiment (APEX) at the time for the Conference.
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| 48. |
- Nyström, Olle, 1979, et al.
(författare)
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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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| 49. |
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| 50. |
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