Circular Eleven Feed with Significantly Improved BOR1 and Aperture Efficiency Over 1.3-14 GHz

A new decade bandwidth circular Eleven feed for future radio telescope projects has been developed, with a significantly improved BOR 1 efficiency (therefore aperture efficiency). This Eleven feed is constructed of "circularly" curved folded dipoles on a flat printed circuit board (PCB), with the aim to make this antenna structure more rotationally symmetrical at a very low manufacture cost. The simulated results show that the BOR 1 efficiency of the circular Eleven feed achieves better than 1 dB over a decade bandwidth of 1.3-14 GHz, which is considered as a significant improvement for decade-bandwidth feed technology

Compact dual-polarized 1.2 - 10 GHz eleven feed by folding outer elements for large decade-bandwidth radio telescopes

The Eleven antenna is a log-periodic folded-dipole-pair array which has two unique radiation characteristics: constant beamwidth and fixed phase center location over decade bandwidth. Therefore, the Eleven antenna is very suitable as a feed for reflector antennas. This paper presents a new compact design of 1.2 - 10 GHz Eleven antenna by folding down the outermost elements of the array. By doing so, it is possible to put the Eleven feed inside a compact cryostat, which is critical for applications in radio telescopes. The new compacted Eleven antenna has only 40% volume of the original standard Eleven antenna with similar performance. Simulations and measurements have verified the design and are presented in the paper

The Circular Eleven Antenna: A New Decade-Bandwidth Feed for Reflector Antennas With High Aperture Efficiency

Future ultra-wideband (UWB) radio telescopes require UWB feeds for reflector antennas, and many new UWB feed technologies have gained substantial progress to satisfy the tough specifications for future radio telescope projects, such as the square kilometer array (SKA). It has been noticed that, different from traditional narrow-band horn feeds, all UWB feeds are non-BOR (Body of Revolution) antennas. Therefore BOR1, efficiency becomes an important characterization for the modern UWB feed technologies. We present a novel circular Eleven feed, constructed of "circularly" curved folded dipoles printed on flat circuit boards, in order to have high BOR1 efficiency at a low manufacture cost. The Genetic Algorithm (GA) optimization scheme has been applied to the design for achieving a low reflection coefficient. Simulated and measured results show that the circular Eleven feed has a reflection coefficient below -6 dB over 1.6-14 GHz and below -10 dB over 78% of the band, and an aperture efficiency higher than 60% over 1-10 GHz and 50% up to 14 GHz

A Compact Dual-Polarized 4-Port Eleven Feed with High Sensitivity for Reflectors over 0.35-1.05 GHz

We present significant improvements to the circular Eleven feed technology for a dual-reflector system operating over 0.35-1.05 GHz as a backup for the square kilometer array (SKA) project Band 1. In this work, the number of the feed ports is reduced to 4 from the previous 8 for dual polarization using a novel geometry at the center. The design is carried out by optimizing with a social civilization algorithm. The resulting improvements include a reflection coefficient below -12dB, an aperture efficiency above 70% at the upper end of the band, a maximum cross-polar level under -15dB, and an ohmic loss about 0.05 dB. A prototype based on this design has been manufactured and the design simulations have been verified against measurements. A simulated sensitivity of the dual-reflector receiver system for the SKA project based on the measured data is also presented in this communication

Onsala Space Observatory - IVS Technology Development Center

We report 2012 activities and plans for 2013

Ultra-wideband feed systems for the EVN and SKA - evaluated for VGOS

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

Wideband single pixel feed system over 4.6-24 GHz for the Square Kilometre Array

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

Cryogenic Integration of the 2-14 GHz Eleven Feed in a Wideband Receiver for VLBI2010

The next generation VLBI systems require the design of a wideband receiver covering the 2-14 GHz range, necessitating a wideband feed. Presented here are the 2009 development of a cryogenic 2-14 GHz Eleven feed for reflector radio telescope antennas, including its integration into a cryogenic receiver. The Eleven feed is designed for dual linear polarization and consists of four log-periodic folded dipole arrays. Each pair of arrays is fed by a differential two-wire transmission line connected either to balun or a differential LNA. The present configuration has been measured in many configurations, at various independent labs - corresponding simulations have been done. The results show (across the band) a high polarization efficiency for the feed, with a nearly constant beam width, a reflection coefficient below -10dB, and a constant phase center. Electrical parameters under cryogenic conditions and measured receiver noise temperatures are presented

Onsala Space Observatory – IVS Technology Development Center Activities during 2017–2018

We give a brief overview of the technical development related to geodetic VLBI done during 2017 and 2018 at the Onsala Space Observatory

Sensitivity simulation and measurement of the SKA Band 1 wideband feed package on MeerKAT

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