Uncrewed Systems Technology 046

105 GNSS | Focus within a 5 x 5 mm space while featuring an integrated RF front end is therefore something of a holy grail for transponder developers. Achieving this in a small space is not easy: proper physical separation between high-sensitivity RF front ends and super-fast signal processors is key to achieving satisfactory results. One patented approach combines an FPGA with a microcontroller that has an integrated high-speed analogue- to-digital converter. That reduces the size of the system as well as the noise floor, without requiring high computing power. And because the GNSS it uses consumes only 12 mW of power, it keeps the approach energy-efficient while also providing fast signal processing – fast enough to effectively decode the full bandwidth of ADS-B in real time. Future solutions aimed at conforming with FAA and other aviation authorities’ requirements on remote ID (which have been made mandatory on all commercial UASs produced in the US as of September 15 this year) are expected to provide more and more combinations of GNSS, Bluetooth and wi-fi. One or two solutions aimed at fusing these in particularly small packages are already available, despite the physical challenges that poses in terms of antenna separation and the necessary filtering against unwanted saturation and out-of-band frequency interference. Future prospects Although the challenges to stable, reliable GNSS operations are growing, so too are the technological and infrastructural advances needed to support them. As well as board-level hardware and software improvements, more and more advanced satellites are to be launched over the course of this decade, including GPS L5 and L1C, and others across various constellations. And while still indispensable to almost all uncrewed systems in and around the world, GNSS is only one of many radio technologies that suppliers to the autonomous world have developed. Being able to use other emitters for positioning alongside GNSS, whether designed with that intent or not, presents increasingly attractive propositions for safe and stable navigation. Precise relative positioning is key to so many uncrewed vehicles, and synthetic aperture radar, Lidar, inertial aiding and more create opportunities for robust blended positioning solutions. Turning experimental combinations of these into commercial products, and making them accessible for useful applications, can be both the most difficult and rewarding thing that developers are now attempting. A final note on the future of GNSS constellations concerns GLONASS. While long-established as a standard across solutions from various manufacturers, and commonly packaged alongside GPS in dual-frequency receivers for several years now, many developers are increasingly wondering if it makes sense to include the Russian satellite group for position calculations. Since the invasion of Ukraine, some companies that provided critical laser ranging and positioning services for GLONASS satellites have terminated their contracts, and it is difficult to predict exactly what impact that will have on positioning accuracy, and for how long. More and more GNSS equipment customers are therefore asking about satellite constellations, and increasingly indicate a preference for working with the Galileo constellation instead. The longer the war in Ukraine goes on, the longer Galileo’s rise should be expected to continue. Acknowledgements The author would like to thank Giri Baleri and Ed Norse at Trimble, Philip Rowse at CubePilot, Ryan Braun at uAvionix, Chris Shaw at Advanced Navigation, Rafal Osypiuk at Aerobits, Robert Orr at Arralis, Abhijeet Bokil and Sandip Aghav at Aeron Systems, and Matt Steele and Kirk Burnell at Hemisphere GNSS for their help with researching this article. Uncrewed Systems Technology | October/November 2022 Future uncrewed traffic management could depend on high-end combinations of GNSS, wi-fi and Bluetooth (Courtesy of Aerobits) Optimising an INS requires fine-tuning its Kalman filter for its different hardware components, vehicle platform and expected mission parameters (Courtesy of Aeron Systems)