This paper describes the study of a novel dual-band antenna dedicated to be mounted on a helicopter for emergency localisation of cellular phones within the framework of the RNRT project called LUTECE. A folded dipole placed on a limited ground plane to allow wideband functionality and good radiation characteristics is proposed. Starting from this new topology, a directive array for the emission part and a circular disposition of five radiating elements with separated outputs for the receiving part are studied. All these developments are performed using our simulation code (FDTD method) along with experimental studies.