Expanding GNSS Testing with Multiple Synchronized Signal Recorders

Iurie Ilie and Stephane Hamel

Abstract:	Record and playback systems bring valuable real-world test conditions into the lab because simulation is not enough to fully test some applications: they often require real-world signals and conditions to complete the test and validation processes. Thus, record and playback systems are recognized as precise and necessary tools during much GNSS receiver testing and validation, and they can significantly reduce the amount of time and resources required for those phases. Given the complexity of the GNSS spectrum, recorders used in the field should handle wideband signals as well as multiple carriers. For example, the GNSS spectrum covers the frequency band from 1164MHz to 1300MHz in the lower L band and from 1559MHz to 1610MHz in the upper L band. Inside this frequency band, a multitude of signals belongs to different satellite constellations such as GPS, GLONASS, Galileo, and Compass. To be able to efficiently record and play back all these signals, one needs an extremely wideband recorder or a multi-channel record and playback system with tight channel synchronization. As well, to synchronously record the GPS L1 and L2 bands, one needs two recording channels (since GPS L1 and L2 frequencies are separated by more than 300MHz). In the same way, to cover the GPS L1, L2 and L5 bands, three channels are required. In some applications, the receiver is connected to multiple and/or multi-element antennas to take advantage of antenna selectivity or a multiple input approach (e.g., attitude control, beam steering). This approach requires even more recording channels to process the signal in a synchronous and coherent way. To solve this synchronization and coherency challenge, Averna has developed a new software/hardware architecture that allows control and tight synchronization between multiple recording channels and multiple recording systems under the 1 nanosecond (ns) level. When Averna’s RP-5300 two-channel recorder is used, the architecture allows multiple RP-5300 chassis interconnections to form 4, 6, 8 or even more recording channels to operate in a synchronous and coherent way. Another feature of the architecture is the ability to control and synchronize multiple recording systems that are geographically separated. This is useful for Differential GNSS applications where the distance between the base and rover can reach tens of kilometers or even more. In fact, there is no limit to the distance that may separate multiple recorder systems, since the control is done over the Internet and all systems are synchronized with the unique GPS time reference.
Published in:	Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012) September 17 - 21, 2012 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	113 - 117
Cite this article:	Ilie, Iurie, Hamel, Stephane, "Expanding GNSS Testing with Multiple Synchronized Signal Recorders," Proceedings of the 25th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2012), Nashville, TN, September 2012, pp. 113-117.
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