A Galileo E1b,c RF front-end for Search-and-Rescue applications

The current Search-and-Rescue (SAR) service, which is based on the Cospas-Sarsat system, suffers from major limitations such as poor position accuracy, long alert times and high false alarm rate. Two types of distress signals are used, the 121.5MHz/(up to 100mW) signal and the 406.8MHz/5W signal, the latter being able to carry digitally encoded data, such as the beacon’s position. As a consequence, most distress beacons available today contain a GNSS receiver in order to be able to include the position into the distress message. Galileo will importantly contribute to the improvement of the SAR system. Indeed, the Galileo satellites will include a transponder in order to re-broadcast the 406.8MHz message, which will allow a better coverage of the earth (27 Galileo satellites plus the current seven Cospas-Sarsat satellites) and also a shorter alert time. They will also include a return link message (RLM) in the Galileo E1b open service signal, which will reduce the number of false alarms. Galileo is therefore a great opportunity for the development of a new generation of beacons which will include a Galileo receiver and therefore be able to take advantage of the better coverage provided by the Galileo constellation to provide shorter alert times and of the RLM to reduce the number of false alarms. One of the major issue when designing a Galileo receiver to be operated in a distress beacon is to design a front-end that is sensitive enough to pick the very weak E1b signal in the presence of the strong distress signals. Indeed, in order to receive the RLM message, the Galileo receiver will have to track E1b while the distress signals are emitted. This paper presents a Galileo radio frequency front-end designed in order to operate in the presence of such signals.