Thanks to their unique features, antenna arrays find applications in many scientific and practical areas related to the Earth and space observations, including radio astronomy, water management, weather forecasting and traffic control. Novel digital antenna-array technologies have already resulted in safer cars that employ radars to detect obstacles and other vehicles, and hold the promise to greatly enhance our knowledge of Cosmos and Earth processes with the aid of the giant radio telescopes consisting of 100-1000 antenna array elements (receptors).
The first pioneering new-generation array telescope in Europe −the LOw Frequency ARray (LOFAR) (10 MHz – 250 MHz) − has recently become operational and represents a network of stations located in several countries. The International LOFAR telescope is operated by various national LOFAR consortia, including the Netherlands, Sweden, Germany, France, UK, Italy, Poland and a recent new comer, Spain.The 192 radio antennas that make up Onsala’s LOFAR station cover an area the size of a soccer pitch. Part of LOFAR, the world’s largest radio telescope, is the biggest telescope built in Sweden in the last 35 years.
Today, another major international effort of the radio astronomy community is focused on the development of the next-generation radio telescope known as the
Square Kilometer Array (SKA) (300 MHz – 30 GHz). Building the SKA is a large-scale project involving more than 20 countries around the world (including Sweden) which will result in a system 10 times larger than LOFAR.
Figure 3:
An Artist’s impression of the future radio telescope – The Square Kilometer Array (SKA). Three types of the antenna array technologies constitute the SKA hybrid design: (i) ‘Planar Aperture Phased-Arrays’ (AAs) with electronic (digital) beam-steering at low frequencies, similar to LOFAR; (ii) ‘Phased-Array Feeds’ (PAFs) −also named as ‘Focal Plane Array Feeds’− of dish antennas with both electronic and mechanical beam-steering capabilities at the intermediate frequencies; and (iii) ultra wideband ‘Single-Pixel Feeds’ (SPFs) of dish antennas with enhanced mechanical beam-steering at high frequencies.On-going projects:
> The VINNMER project ‘Antenna Systems for the Next Generation Radio Telescopes’
This project is funded by part by the Swedish Agency for Innovation System VINNOVA, Onsala Space Observatory and the Netherlands Institute for Radio Astronomy. At Chalmers, we develop numerical electromagnetic methods for the analysis and design of beamforming active antenna array systems, such as the novel phased array frontend receiver for the Westerbork Synthesis Radio Telescope (WSRT) – named APERTIF. The APERTIF system is being developed by
ASTRON and when operation, it will be capable to enlarge the field of view of the WSRT with a factor 25.
Figure 4: The Artist’s impression of the APERTIF system developed for the Westerbork Synthesis radio telescope comprising 14 large reflector antennas, each equipped with the novel digital phased array feed. When operation, the APERTIF feed will enlarge the field of view of the present system with a factor 25. (Credits: ASTRON.)Figure 5: The numerical model of the APERTIF phased array antenna feed consisting of 121 electromagnetically coupled antenna elements.
Researchers: Dr. Ivashina, PhD student Oleg Iupikov
Project duration: 2010-2012
> PhD student project ‘Advanced methods for the electromagnetic analysis of complex antenna array systems and radio astronomy imaging’
This project is funded by the Swedish Research Council and performed in collaboration with the Stellenbosch University (South Africa), the Netherlands Institute for Radio Astronomy and Brigham Young University (the USA). We develop (i) numerical methods and simulation software tools for modeling the performance of the overall antenna system including the effects of mutual interaction between different components; and (ii) antenna array signal processing algorithms for fast imaging of large-scale areas on the sky.
Figure 6: The simulated mutual interaction effects (so-called standing wave effects) between the feed and reflector antenna.
Figure 7: The electromagnetic model of the phased array feed having 121 reception functions, in the focal region of a large reflector antenna.
Researchers : PhD student Oleg Iupikov, Dr. Marianna Ivashina and Dr. Rob Maaskant
Project duration: 2011-2016
> Electromagnetic Analysis of the Ultra Wideband Multi-Port Eleven Antenna for the SKA Dish Array
This project is funded by Onsala Space Observatory and is aimed at the analysis of the Eleven feeds for different types of the reflector antenna systems such as being considered for the SKA. The Eleven feed has been invited by Prof. P.-S. Kildal (Chalmers).
Figure 8: The Off-set Gregorian reflector antenna (one of the SKA dish designs), equipped with the UWB Eleven antenna feed.
Figure 9: The numerical simulation of the SKA reflector antenna reception function when observing the sky at different antenna pointing directions
Researchers : Master student Wan-Chun Liao, Dr. Marianna Ivashina and PhD student Oleg Iupikov
Project duration: 2011-2012
> System noise performance of the 2-14 GHz cryogenic Ultra Wideband Feed Receiver for the SKA Dish Array
This project is funded by Onsala Space Observatory and the Prof. Kildal’s SIDA grant. It is performed in collaboration with Wits University (South Africa) and is aimed at the development of the receiver. This study includes both the numerical analysis of the co-integrated antenna-receiver design and experimental verification.
Researchers : PhD student Benjamin Klein, Dr. Marianna Ivashina, Dr. Rob Maaskant and Dr. Miroslav Pantaleev.
Project duration: 2011-2014