GARDA consortium at the Final Presentation
The GARDA Project: Building a Galileo Receiver
The long history of the Galileo program’s development has tended to focus on the design, construction, and launch of the system’s satellites. But an equally important activity is the development of Galileo-capable user equipment. Leaders of an engineering team that has developed a multi-frequency Galileo receiver describe their efforts and the results.
As Galileo satellites begin reaching orbit and transmitting their signals, a critical complement needs to be in place for the user community: Galileo-capable receivers.
In the frame of Europe’s development of Galileo, the Galileo Joint Undertaking (GJU) has issued three calls since 2003 under the European Commission’s 6th Framework Program to study, design, and develop the essential technologies, components, applications, and services for the Galileo user segment.
In response to the first call, Alcatel Alenia Space Italia (AASI) was selected to lead a consortium responsible for developing Galileo receiver technologies within the (GAlileo user Receiver Development Activities (GARDA) program.
Within the GARDA project, AASI has developed a prototype receiver capable of processing L1, E5a/E5b, and E6 Galileo signals in addition to GPS L1. This represents one of the first GPS/Galileo receivers. In developing this prototype receiver, efforts have been made to define the architecture of the RF front-end and baseband sections to be as flexible as possible.
The aim of the GARDA project was to develop a modular architecture that could be the basis for future AASI GPS/Galileo receiver products and prepare the way for user receivers to be “ready on the market” when the Galileo system becomes operational.
The design flexibility also allows a quick reaction to the evolution and changes in the Galileo signal specification.
In particular, the GARDA design is the basis for the on-going development of a safety-of-life (SoL) receiver within the GJU’s Galileo Integrity Receiver for Advanced Safety Of Life Equipment (GIRASOLE) project. Further, GARDA receivers are going to be used within the Galileo receiver chain of the ground mission segment sensor stations to feed data to the Galileo orbit determination, integrity and timing facilities.
The GARDA project has also provided the opportunity to analyze future market of Galileo applications, to study some core receiver processing techniques and also to develop two important components such as the Galileo RF signal simulator as well as a complete Galileo receiver and environment SW simulation tool.
This article will describe the design and testing of the receiver technology developed under the GARDA program. We will begin by describing the design challenges and core technologies identified as crucial for receiver development. Then we will address the receiver architecture, functions, and designs developed and tested in a prototype system before implementation in the final product.
A section of the article addresses the development of two GNSS simulators as part of the GARDA initiative. These simulators were used to help in test-bench design and development of the receivers as well as in testing and performance verification, along with commercial simulators. The article will conclude with a discussion of key results from test evaluations of the GARDA receiver.
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Receiver Architecture and Functions
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Antenna and Front End
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Digital Signal Processing
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Galileo Mono Channel RF Simulator
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GARDA Receiver Test Results
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• the GIRASOLE Safety of Life receiver will be the pre-cursor of a combined GPS/Galileo receiver product to be used in rail, aviation, and maritime applications. First demonstrations are expected to be carried-out in the frame of the GJU second call for the GRAIL project for rail applications
Furthermore, the software simulator toolkit as well as the Galileo RF signal simulator are available to Galileo receiver and user applications and will be further improved to incorporate additional features.
For the complete story, including figures, graphs, and images, please download the PDF of the article, above.
The Galileo Receiver Analysis and Design Application (GRANADA) simulation toolkit from Deimos Space, Madrid, Spain, with its Bit-True GNSS Receiver Simulator and Environment and Navigation Simulator has provided design and testing support throughout the GARDA project.
The Galvani IC was implement on Virtex2 and/or Virtex4 FPGAs from Xilinx, Inc., San Jose, California, USA. In the GARDA configuration, the digital correlation blocks (GALVANI channels) have been developed in VHDL on a Virtex-II XC2V8000 FPGA from Xilinx, while signal processing algorithms run on Analog Device ADSP-21060 SHARC from Analog Devices, Inc., Norwood, Massachusetts, USA. The digital section includes an Analog Devices ADSP21x60 digital signal processor that runs all the acquisition signal processing and tracking loops software. The ADCs used are AD9480, also from Analog Devices.
The GMCS DAC board assemblies are based upon the DSP Builder development tool from Altera Corporation, San Jose, California, USA. The GMCS test configurations used a 20 Gsps true sampling scope from Tektronix Inc., Beaverton, Oregon, USA, and an HP 16500C Logic Analysis System from Agilent Technologies, Santa Clara, California USA.
The GARDA receiver was tested using Spirent 4500 and 7700 GPS simulators and the Spirent Prototype 7800 Galileo simulator, Spirent Communications, Paignton, Devon, England, as well as the Galileo Mono Channel Simulator developed in the frame of the GARDA program by Space Engineering, of Rome, Italy.
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