A Galileo E1b,c RF Front-End Optimized for Narrowband Interferers Mitigation

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 first 121.5MHz/(up to 100mW) and the second 406MHz/5W, the latter being able to carry digitally encoded identification and position data. The Galileo system will importantly contribute to the improvement of the SAR system. Indeed, the Galileo satellites will include a transponder in order to re-broadcast the 406MHz message, which will allow a better coverage (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. The Galileo system 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 distess beacon is to design a front-end that is sensitive enough to pick the very weak Galileo signals and on the same time rejects the strong distress messages. Indeed, when the beacon is turned on, the Galileo receiver is in cold start conditions and a short amount of time is left to the receiver to get a first fix before any distress message is actually emitted. However, in some cases, the receiver is not able to determine its position sufficiently fast and the front-end therefore has to acquire the satellites in the presence of the distress signals. This paper presents a Galileo radio frequency front-end designed in order to operate in the presence of such signals.