The Art of ARTUS–A Second-Generation Galileo/GPS Receiver

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Europe’s Galileo program is seeking to accelerate receiver technology development even as the space and ground segments of the system are being implemented. A group of companies have collaborated on development of a geodetic-grade Galileo-GPS receiver: ARTUS. The engineering team in charge of the project describes their work to date, including tests that tracked signals from China’s Compass system as well as GIOVE-A and GPS.

Thorsten Lück, Jon Winkel, Michael Bodenbach, Eckart Göhler, Nico Falk, Angelo Consoli, Francesco Piazza, Danilo Gerna, Robin Granger, Peter Readman, Steve Simpson, and Hans-Jürgen Euler

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Creation of new global navigation satellite systems and modernization of existing ones is introducing many new signals across a wide swath of RF spectrum now and in the near future. These developments are accompanied by a growing need to design new GNSS receivers that can work with new signal structures on an increasing number of frequencies.

Europe’s Galileo program has supported a number of activities intended to promote innovations in receiver design, such as prototype Galileo user equipment, reference receivers, and so on.

One such activity is a project named ARTUS (Advanced Receiver Terminal for User Services), 50 percent of which is financed by funds allocated by the Galileo Joint Undertaking (GJU). A consortium of four companies is leading the ARTUS project (see "Acknowledgments" below)

ARTUS supports the development of receiver technologies to aid the research and development activities for Galileo “professional” receivers. These efforts are designed to facilitate the availability of Galileo professional receiver prototypes and antennas at an early stage.

ARTUS provides Galileo/GPS navigation capability. All three Galileo frequencies (L1, E6 and E5a/E5b) are supported as well as the GPS L1, L2 and L5 (L5=E5a) frequencies.

The receiver supports any BPSK (GPS-C/A, Galileo E5a and E5b (sideband tracking), AltBOC (E5ab), Galileo L1-B/C (BOC(1,1)) as well as BOCc(15,2.5) (E1-A / E6-A); GIOVE-A transmits BPSK (E5a/E5b/E6) and BOC(1,1) (E1).

Although the receiver can track the modulations foreseen for the PRS, it cannot generate the corresponding codes. One can, however, do performance measurements using periodic substitute codes.

Although not initially planned, the consortium has decided to also implement the GPS L2 band for commercial reasons. The unit performs the measurements and processes the raw data to provide an RTK solution.

The Artus design will also form the basis for a breadboard development of the next generation RIMS receivers. This development will be conducted in the frame of an ESA contract lead by IFEN with NemeriX and Euro Telematik as subcontractors.

This article describes the design and operation of the second-generation ARTUS receiver with a particular focus on innovations in four key areas: antenna, RF front-end, digital baseband processing, and navigation software.

Although originally intended to focus primary on tracking Galileo and GPS signals, the flexible design of ARTUS also allows it to receive and track signals from the Russian GLONASS system and China’s Beidou.

After discussing the receiver design and operation, we will briefly describe some of the results of testing using combinations of laboratory GNSS signal simulators, signals-in-space, and simulated signals generated in the German Galileo Test Bed (GATE). . .

Conclusion
The ARTUS GNSS receiver described in this article offers a rich flexibility for various configurations of signals on different RF bands. The high performance antenna in conjunction with a flexible RF front-end design offers excellent performance on all currently available GNSS signal bands, including the upcoming Galileo system.

With the availability of up to 120 channels, the receiver is well equipped for future navigation systems; however, it can also be configured in a version with only 20 or 40 channels for tracking the currently available GPS (L1 and L2) alone.

The modular concept, applied even for the firmware of the baseband processor FPGAs, allows easy adaptation of the algorithms developed for the ARTUS receiver or fast implementation of new algorithms. And if the IP protocol is used, any user interface can easily connect — even remotely — to the receiver — whether for navigation or monitoring purposes.

The ARTUS project is now in its qualification phase. Further developments aim for the commercialization of the receiver.

(For the complete article, including figures, charts, and images, please download the PDF version at the link above.)

Acknowledgments
ARTUS was developed in the framework of a GJU 50 percent–funded project, contract GJU/05/2414/CTR/ARTUS. These activities have been taken over by the European GNSS Supervisory Authority (GSA). This support is gratefully acknowledged. IFEN served as the principal contractor for ARTUS.

The consortium members involved in the ARTUS receiver development are ifEN (overall system design and baseband processing), NemeriX (analog RF-front-end), Roke Manor Research (antenna and RF splitter), Leica Geosystems and inPosition (RTK software). In essence the ARTUS design is based on previous receiver developments carried out by IFEN in the frame of the German Galileo Test Bed (GATE).

GATE is being developed on behalf of the DLR (German Aerospace Center, Bonn-Oberkassel) under contract number FKZ 50 NA 0604 with funding by the BMWi (German Federal Ministry of Economics and Technology). DLR kindly gave its permission to publish the preliminary test results.

Manufacturers

The RF ASIC used in ARTUS is the NJ1008 from NemeriX, Manno, Switzerland; the earlier generation RF ASIC is the NemeriX NJ1007. The simulated GNSS signals were generated by a NavX-NCS from IfEN GmbH, Poing, Germany. The ARTUS receiver integrates the TRI-G07 antenna from Roke Manor Research Ltd., Romsey, Hampshire, United Kingdom, Virtex5 FPGAs from Xilinx, San Jose, California, USA, and ADF4110 PLLs from Analog Devices, Norwood, Massachusetts, USA. The medium- and low-speed baseband processing following signal conditioning is executed on Xilinx Microblaze soft-core CPUs. Figures 8 and 9 are displayed on Google Maps by Google Inc., Mountain View, California, USA.

Author Profiles

Thorsten Lück studied electrical engineering at universities in Stuttgart and Bochum and received a Ph.D. (Dr.-Ing.) from the University of the Federal Armed Forces in Munich. Since 2003 he has worked for IfEN GmbH in receiver technology division as the head of R&D embedded systems.

Jon Winkel has been the head of receiver technology at IFEN GmbH since 2001. He studied physics at universities in Hamburg and Regensburg and received a Ph.D. (Dr.-Ing.) from the University FAF Munich, where his studies focused on GNSS modeling and simulations.

Michael Bodenbach has studied communications engineering at the University of Applied Sciences in Braunschweig/Wolfenbüttel. Since October 2003 he has worked in the receiver technology department at IFEN GmbH focusing on hardware and FPGA development.

Eckart Göhler received his Diploma in physics from the University Tübingen and his Ph.D. from the Institute for Astronomy and Astrophysics, Tübingen. Today he works as a system engineer at IFEN GmbH.

Nico Falk received his Diploma in electrical engineering from the University of Applied Sciences in Offenburg, Germany. Since then he has worked at IFEN GmbH.

Angelo Consoli received the Dipl.-Ing. degree in electrical engineering from the Swiss Federal Institute of Technology (ETH), Zurich. Since 1993 he has been professor for telecommunications and security at the University of applied Science of Southern Switzerland. Since 2001 he has also been aerospace program manager at NemeriX.

Danilo Gerna is principal RF designer at NemeriX. He received the degree of engineering (summa cum laude) from the University of Pavia, Italy. He joined NemeriX SA in 2005 where he is involved in high-performance, low-power RF/analog design for satellite navigation applications.

Francesco Piazza is chief scientist at NemeriX SA. He received the Dipl.-Ing. degree and Ph.D. in electrical engineering from the Swiss Federal Institute of Technology (ETH), Zurich. In May 2000 he founded TChip/NemeriX SA, where he is responsible for analog and RF IC design.

Robin Granger attained a master’s degree in electronic engineering from Southampton University and now works for Roke Manor Research Ltd., Romsey, Hampshire UK, as a consultant engineer in the electromagnetic engineering group.

Peter Readman graduated from Imperial College London in 1986 with a degree in physics. He joined Roke Manor Research Ltd. in 1995 and now works as a consultant engineer in the electromagnetic engineering group.

Steve Simpson graduated from the University of Salford with a degree in electronics and went on to gain a P.hD. from Sheffield. He currently leads the electromagnetic engineering group at Roke Manor Research Ltd.

Hans-Jürgen Euler has worked for more than 20 years in the area of precise GNSS positioning. For more than 15 years he developed real-time algorithms at Terrasat (now Trimble) and Leica Geosystems. Euler now works in consulting and development as a GNSS specialist for his company, inPosition gmbh.