A Unique Software GPS Receiver and Simulator Platform for Clock Error Measurement and Simulation

Yanhong Kou, Yue Jiao, and Yu T. Morton

Abstract:	Oscillator frequency instabilities can be measured using a GPS receiver by exploiting the stable GPS time scale. A software GPS receiver is cost-effective and flexible, and can be easily integrated into system equipment to meet the needs of a variety of applications. Considering different impacts of clock errors on hardware and software correlator-based receiver, this paper develops a software GPS receiver method to continuously measure short-interval oscillator frequency fluctuation. To validate its performance, the frequency fluctuation is further incorporated into a software GPS constellation simulator. The close-loop results show that the receiver can precisely extract the clock error injected into the simulated digital IF signals, with a resolution of 2.5E-11/20ms for the raw clock frequency measurement, and 2E-12/20ms for the filtered measurement. The paper presents signal processing strategies in the presence of clock frequency offset, formulates both the frequency error extraction in the software receiver and the signal model integrating clock errors into the simulator, and introduces an unbiased FIR filter to filter out the high frequency noise component in the clock error measurement. The measurements for a Rb clock, an OCXO, and a TCXO using live GPS signals, as well as the close-loop test results will be presented to demonstrate the feasibility and effectiveness of the unique software receiver and simulator platform for clock error measurement, characterization, and simulation.
Published in:	Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011) September 20 - 23, 2011 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	2923 - 2930
Cite this article:	Kou, Yanhong, Jiao, Yue, Morton, Yu T., "A Unique Software GPS Receiver and Simulator Platform for Clock Error Measurement and Simulation," Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011), Portland, OR, September 2011, pp. 2923-2930.
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