The engineering team behind the signal technology underpinning Europe’s Galileo satellite global navigation system has reached the final of this year’s European Inventor Award, after the European Patents Office nominated a team led by Spanish engineer José Ángel Ávila Rodríguez (now part of ESA’s Galileo team) and his French colleague Laurent Lestarquit (from France’s CNES space agency).
The engineers, who had previously worked together as members of the multinational Galileo Signal Task Force, came up with a pair of innovative signal modulation techniques to pack multiple Galileo signals together, allowing them to simultaneously serve different sets of users while boosting “signal performance and robustness”. Both innovations have been adopted by Galileo and are in use today.
The first technique, called Alternative Binary Offset Carrier modulation (AltBOC for short), combines four signals into one large one, resulting in the widest bandwidth navigation signal ever transmitted. Two of these signals are sitting on a ‘carrier’ named E5a, while the other two are on the carrier E5b.
José Ángel said: “AltBOC is a way of transmitting four components in a very wide bandwidth signal, using a single radio frequency chain on the satellite in an intelligent way, where originally two chains would have been needed to transmit in two separate frequency bands — E5a and E5b. The result is a frequency-rich signal that fundamentally improves positioning performance and robustness.”