EFFICIENT DUAL-BAND PLANAR ARRAY SUITABLE TO GALILEO P.Valle, A.Netti, M.Zolesi and R.Mizzoni (1) , M.Bandinelli, R.Guidi (2) (1) Alcatel Alenia Space Italia, via Saccomuro, 24, 00131 Roma, Italy, paolo.valle@aleniaspazio.it (2) IDS Ingegneria Dei Sistemi, via Livornese 1019, Pisa, Italy, r.guidi@ids-spa.it ABSTRACT An optimum dual band self-diplexed antenna, particularly suitable to accomplish the demanding requirements of the European Navigation System (GALILEO) is highlighted. The antenna relies on the key enabling technologies previously developed for the pioneering GIOVE-A satellite (Galileo In Orbit Validation Element) successfully flown on 28 December 2005. Its excellent operational status and the quality of transmitted signal are a validation of the technology solutions adopted to the antenna. Both GIOVE-A and the enhanced design will be described, in particular the solutions adopted to improve the overall performance Vs Galileo. 1. GIOVE-A GIOVE-A (Galileo In Orbit Validation Element) is the first satellite of the future European GPS constellation GALILEO. The NAVANT (NAVigation ANTenna) developed by AAS-I (Alcatel Alenia Space Italia) is a key point of GIOVE-A satellite. On 12 January 2006, the first Galileo navigation signals were successfully transmitted by GIOVE-A positioned at a MEO orbit of 23000 Km about. Figure 1. GIOVE-A (artist's impression: ESA) The FM unit is illustrated in figure 2. The antenna is an array of 36 self diplexed and stacked patch radiators fed by two independent beamforming networks (BFN’s) operating at low and high frequency band respectively. Array grid is a mixed lattice, optimized for the dual band functionality. Figure 2. GIOVE-A NAVANT (front) The antenna design key drivers requirements are hereafter summarized • Dual Band RHCP transmit antenna (1156- 1300/1555-1596 GHz) • Gain: 15dBi at Edge of Coverage (EOC), with isoflux shape in the field of view of +/-12.2° and admissible ripple of 2 dB • Axial Ratio: < of 1.5 dB • Phase Center and Group Delay Stability : ±5mm and 50ps respectively • Stiffness : > 100 Hz • Mass : 16 Kg The adopted technological solutions and the key design and optimization rules shall be shown. 1.1 Array Layout A major constraint for optimal radiated performance is the dual band requirement that leads to two different array lattices at the two frequency bands, for optimum aperture field distribution. A regular dense array grid is not so effective since to realise the isoflux beam only two regions are active: the inner one where the power is mainly concentrated and the outer region, with elements out of phase wrt the inner part, to realise the isoflux beam and requested flat phase in the far-field. _____________________________________________________ Proc. ‘EuCAP 2006’, Nice, France 6–10 November 2006 (ESA SP-626, October 2006)