ION Technical Content
Rapid Parallel GPS Signal Acquisition
| Abstract: | A GPS acquisition system which achieves extremely short search times is presented. The system requires no prior knowledge of position or time. Using a 50MHz clock frequency, 25 satellites can be searched in parallel. Under nominal signal conditions, two-second search times have been demonstrated. The acquisition unit performance has been verified both with live satellites as well as with a GPS simulator. With the GPS simulator the performance with weaker signal conditions was also evaluated. The acquisition threshold was found to be −134 dBm with a RF noise figure of 4 dB. The developed acquisition system is based on parallel matched-filter implementation, which is capable of searching code offsets of a number of satellites simultaneously. The frequency domain is searched by sweeping a common local oscillator frequency. The search process is controlled by a state machine, which has a number of parallel channels, each capable of performing a search of its corresponding PRN code. This implementation is considerably more effective than performing sequential search of each satellite signal. The modest hardware complexity increase and the search speed improvement compared to the single-satellite search unit makes the parallel architecture attractive. The advances in current CMOS manufacturing technologies make fully digital implementation of a matched filter based acquisition unit economically possible even for low-cost GPS receivers. The acquisition system has been implemented in 0.35 µm CMOS process. A sensor GPS receiver containing the acquisition unit, 12 channel correlating receiver together with the DSP and SRAM memory for running the tracking algorithm fits in a single chip and is packaged in a 64-pin LQFP package. |
| Published in: |
Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT |
| Pages: | 810 - 816 |
| Cite this article: | Eerola, Ville, "Rapid Parallel GPS Signal Acquisition," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 810-816. |
| Full Paper: |
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