| 11. |
- Flygare, Jonas, 1988, et al.
(author)
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Beyond-Decade Ultrawideband Quad-Ridge Flared Horn With Dielectric Load From 1 to 20 GHz
- 2023
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In: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 71:3, s. 2110-2125
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Journal article (peer-reviewed)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.
(author)
-
BRAND: Ultra-Wideband Feed Development for the European VLBI Network - A Dielectrically Loaded Decade Bandwidth Quad-Ridge Flared Horn
- 2018
-
In: IET Conference Publications. - : Institution of Engineering and Technology. ; 2018:CP741
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Conference paper (peer-reviewed)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.
(author)
-
Design trade-offs in feed systems for ultra-wideband VLBI observations
- 2018
-
Conference paper (other academic/artistic)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.
(author)
-
Dielectrically Loaded Quad-Ridge Flared Horn for Beamwidth Control Over Decade Bandwidth-Optimization, Manufacture, and Measurement
- 2020
-
In: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 68:1, s. 207-216
-
Journal article (peer-reviewed)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
(author)
-
Dielectrically Loaded Quad-ridge Flared Horns for Ultra Wideband Reflector Feed Applications in Radio Astronomy
- 2022
-
Doctoral thesis (other academic/artistic)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.
(author)
-
Integrated calibration noise coupler for room temperature SKA band 1 feed system
- 2017
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In: 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
-
Conference paper (peer-reviewed)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.
(author)
-
Sensitivity and Antenna Noise Temperature Analysis of the Feed System for the Onsala Twin Telescopes
- 2017
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In: 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
-
Conference paper (other academic/artistic)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.
(author)
-
Sensitivity simulation and measurement of the SKA Band 1 wideband feed package on MeerKAT
- 2019
-
In: 13th European Conference on Antennas and Propagation, EuCAP 2019. ; EuCAP 2019
-
Conference paper (peer-reviewed)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.
(author)
-
Strategy and Overview for Development of Beyond-Decade-Bandwidth Quad-ridge Flared Horns for Radio Astronomy
- 2021
-
In: 15th European Conference on Antennas and Propagation, EuCAP 2021.
-
Conference paper (peer-reviewed)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
(author)
-
Ultra-wideband feed design and characterization for next generation radio telescopes
- 2018
-
Licentiate thesis (other academic/artistic)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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