[1] Univ Oviedo, Dept Elect Engn, Gijon, Spain
[2] Inst Telecomunicacoes IT, Lisbon, Portugal
[3] Univ Inst Lisbon ISCTE IIJL, Dept Informat Sci & Technol, Lisbon, Portugal
[4] Escola Naval, Ctr Invest Naval CINAV, P-1400203 Almada, Portugal
[5] Univ Lisbon, Dept Elect & Comp Engn, Inst Super Tecn IST, Lisbon, Portugal
[6] European Space Agcy, Antenna & Submillimeter Waves Sect, Noordwijk, Netherlands