Active, electrically scanned array antennas (AESA:s) find applications in various disciplines ranging from radio and radar to astronomy. The main advantage of the AESA is its capability to rapidly switch the antenna lobe between different directions. The applicability has been limited due to costs associated with manufacturing, active electronics, and the requirement of high performance signal processing. The last few decade’s advances in semiconductor technology, passive front-end design, signal processing and material science have made AESAs cheaper and more versatile and AESAs is of interest for wideband base station arrays, integrated multifunctional sensors and multi-beam satellite antennas to mention a few.
In the present project the interest in in sparse/irregular arrays mainly for geostationary satellite application and on mid-size wide-band arrays for communication use. To utilize these emerging techniques, parts of the Swedish antenna industry (RUAG and Ericsson Research) together with KTH and Chalmers foresee an increased need for array antenna research.
Harmonized spectrum world-wide for mobile broadband communication is a vision but scarcely a reality. The mobile broadband operators have to rely on several different frequency bands, often non-contiguous, in order to provide capacity and coverage to the end-users. From a base station antenna perspective, the operators already today faces challenges with more and more antennas mounted at the sites. Current mobile broadband applications aim mainly at frequencies between 700 MHz and 4200 MHz.
Communication via satellites primarily uses reflector antennas on the spacecraft. This has given lightweight simple systems. With the increasing demands on multi-beam with many simultaneous channels, and flexibility in beam shapes, polarization, and power, the reflector systems become big and complicated. The solution is to use direct radiating array antennas, which easily can provide the required flexibility. However, a typical reflector size is 2-3m. A corresponding array would be 1.5 – 2m in diameter, or around 50-100 wavelengths. Even using large elements of two wavelengths diameter, it requires 100-1000 radiators. These radiators need to be active, i.e. include the LNA/power amplifier since the losses in the feed network otherwise would be too large. It is therefore necessary to minimize the number of elements used by exploiting an irregular or sparse spatial geometry of wideband elements without compromising the antenna performance. It is of vital importance for RUAG Space to prepare for this new technology.
To address these issues an improved understanding of antenna elements in a dissimilar surrounding is needed. Application of new approximate calculation techniques is required, as well as experience in antenna element and array design, together with the knowledge of fundamental limitations of antennas. We expect to employ two new PhD students within this field. The combination of the research groups and the active contribution from the industrial partners under Chase opens the road to improving on these antenna challenges.
Coordinator at Chalmers: Dr. Marianna Ivashina
Project leader: Dr. Lars Jonsson, KTH