Antenna Company together with Space Engineering and Airbus in ESA project: Sparse arrays with improved Aperture Efficiency and Scanning Capabilities

The Antenna Company, together with Space Engineering and Airbus, has been awarded a two-year contract by the European Space Agency for the development of next-generation antenna array architectures on conformal shaped host platforms for low / medium Earth orbit (LEO / MEO) satellite applications.

Active phased arrays have been widely studied for satellite applications and space hardware has been mainly developed in Europe for GEO defense applications and LEO/MEO constellations.

In this activity the sparsity of the array should be exploited in order to obtain an improvement, as compared to existing array solutions, in terms of cost and complexity by keeping similar scanning performance or, equivalently, in terms of pattern performance by keeping similar cost and complexity.

Active sparse arrays have been considered especially for GEO missions in Ka-band with limited field-of-view in order to reduce the number of control elements and to increase the DC to RF efficiency of active transmit antennas (by replacing a conventional amplitude tapering with a space tapering). These advantages, combined with recent progresses on HPAs, may enable drastic improvements in multi-beam active arrays.

This activity targets phased arrays able to cover a large field of view as the ones required in LEO/MEO missions. Generally speaking, when increasing the field of view of a phased array, the average dimension of the radiators should decrease and the number of control points should increase. So a priori a lower degree of sparsity may be applied as compared to applications where the field of view is smaller. However, there are still some degrees of freedom and characteristics, which are important for this activity and have not been completely exploited up to now.

A first important trade-off and choice concern the elementary radiator: antenna elements which are ideal to generate a beam close to the boresight direction are not necessarily the preferred ones when the beam has to point far from the boresight direction.

A second important trade-off and choice deals with the 3D or 2D array aperture layout: the best choice for the MEO mission may be not coinciding with the best choice for the LEO mission.

In addition, another element to be considered is the fact that the overall antenna performance, for arrays consisting of not identical radiators, depends not only on the amplitude and phase tapering applied at array aperture level but also on the radiation pattern of the elementary radiators. The individual patterns, which depend on size and excitation of each radiator, provide additional degrees of freedom, which may be exploited during the design stage.

The results of the present activity may find general applicability in several other satellite or ground missions as the ones requiring radars covering a large field of view or on-board antennas for GEO satellites.

The final objective of the project is to design and optimize Sparse Direct Radiating Arrays for Telecom satellite missions with a reduced number of elements, improved aperture efficiency and increased scanning capabilities in order to comply with MEO/LEO mission needs. Improvements shall be proved thanks to the testing of a passive demonstrator of reduced size.

Applicability of the results to GEO missions shall be investigated.

Within said contract, Dr Diego Caratelli, CTO of The Antenna Company is in charge for the deterministic synthesis and design of innovative sparse arrays with enhanced aperture efficiency and wide-angle scanning capability. The manufacturing of a physical demonstrator implementing the developed technical findings is foreseen at the conclusion of the project. The project has started on November 16, 2015 and has to be completed within two years.