An aperiodic active lens for multibeam satellite applications: from the design to the breadboard manufacturing and testing G. Ruggerini 1 , G. Toso 2 , P. Angeletti 2 1 Space Engineering, Via dei Berio 91, 00155 Rome, Italy, gianfranco.ruggerini@space.it 2 European Space Agency, Keplerlaan 1, 2200 AG, Noordwijk, The Netherlands {giovanni.toso, piero.angeletti}@esa.int Abstract— Some advances on the design, manufacturing and testing of an aperiodic bootlace active lens generating a multiple spot contiguous beams coverage are presented in the paper. The antenna represents an interesting architecture based on a single aperture able to replace conventional antennas based on multi reflector dishes onboard geo or non-geo stationary satellites. The antenna has been optimized in terms of number of radiators, dimensions, weight, and power amplifiers efficiency. The first experimental results on a passive antenna system have demonstrated interesting features. The implementation of a real active solution is now on going. I. INTRODUCTION A multibeam antenna based on an active aperiodic lens has been recently presented [1]. The antenna represents a possible alternative solution for realizing, from a geo or non-geo stationary orbit, a multiple spot beams Earth coverage using a single aperture. The future generation of communication satellites will use multi-beam antennas providing wide band two ways communication applications. High gain multiple overlapping spot beams, adopting both frequency and polarisation reuse, will provide the needed coverage. In order to generate several high gain spot beams, electrically large antenna apertures are required. These apertures are today mainly realised by reflectors. Most of the operational or planned multibeam antennas adopt, for up and down links, one feed per beam architecture with adjacent beams generated by different reflectors fed by a cluster of horns. This leads to three to four reflector antennas for European or CONUS coverage receive functions and the same number for transmit [2]. This multiple aperture antenna architecture is the one today usually considered since, when a single aperture is used, inter-feed spacing requirements and feed diameter lead to inefficient illumination of the reflector and insufficient performance in terms of isolation levels. The volume required to accommodate the multi reflectors is very large. Moreover the system does not provide for any flexibility in terms of coverage. A possible solution to generate a multi-beam coverage using a single aperture is the Focal Array Fed Reflector described in [3]. This concept is based on one overlapped beam footprint in the reflector focal plane. This overlapping is performed by connecting together individual feeds using a beamforming network, some of these feeds being used for several beams. This antenna concept is quite complex at focal array level but, with limitation on the maximum number of beams, has the advantage to allow the generation of different beams sizes and shapes with only one aperture. An alternative approach based on a single aperture and consisting in overlapping contiguous feeds in a completely radiative way, i.e. without any bulky beamforming network, has been proposed. Some recent studies [4-7] have demonstrated that this radiative overlapping is achievable using EBG materials or Fabry-Perot resonators positioned in front of an array. All these previous concepts are suitable candidates for multi-beam applications but suffer from different implementation difficulties. In a long term perspective, simpler alternative solutions based on a single aperture are needed. Direct radiating arrays represent also a possible antenna based on a single aperture able to generate the required multibeam coverage. Recently, promising solutions based on aperiodic arrays with equi-fed elements [8-9] have been proposed in order to reduce the complexity and the cost of traditional direct radiating arrays. Active discrete constrained lens antennas permit generating as well a multiple spot beams coverage adopting only a single aperture. However, up to now they have not been considered as a promising alternative solution essentially because of their high volume, weight, deployment issues and thermo-elastic problems [10-12]. Recently, we have been proposing possible solutions in order to drastically decrease the complexity and cost of active constrained lens for multi spot beams applications. The aim of this paper consists in reviewing the main improvements achieved in the design of such a type of EuCAP 2011 - Convened Papers 3855