Doppler Shift Characterization of Chinese Area Positioning System

Meng Wang and Lihua Ma

Abstract:	The Chinese Area Positioning System (CAPS) is a Navigation System based on commercial communication satellites invented by scientists from Chinese Academy of Sciences. Its constellation consists of geostationary Earth orbit (GEO) and slightly inclined geostationary orbit (SIGSO) satellites, which are different from the other navigation satellite system, such as GPS and GLONASS. To achieve centimeter-level ranging accuracy, a triple-frequency signals method for CAPS is proposed to eliminate the ionosphere errors by the chosen phase-code combinations. The optimized three frequencies from C-band are 3826.02MHz, 3979.47MHz and 4143.15MHz. Considering the system specification of CAPS constellation and frequencies, its Doppler characterization is studied. The Doppler shift of two GEO satellites (87.5°E and 110.5°E) and two SIGSO satellites (51.5°E and 142°E) with three optimal frequencies is simulated. Since the Doppler shift is produced by the relative motion of the satellite with respect to the user, the satellite and user position, the direction and magnitude of satellite and user velocity all influence the value of Doppler shift. In the simulation, the satellite velocity vector is computed using CAPS satellites ephemeris information and six CAPS stations are applied as user location. The simulation results show that the Doppler shift of the GEO satellites is no more than ±25 Hz and that of the SIGSO satellites no more than ±600 Hz for the stationary user. When the user velocity is less than 100 m/s, the GEO satellite Doppler shift is limited within ±1.3 kHz and the SIGSO satellite Doppler is within ±1.9 kHz. The Doppler shift of CAPS is mainly caused by the user velocity.
Published in:	Proceedings of the 2013 International Technical Meeting of The Institute of Navigation January 29 - 27, 2013 Catamaran Resort Hotel San Diego, California
Pages:	107 - 111
Cite this article:	Wang, Meng, Ma, Lihua, "Doppler Shift Characterization of Chinese Area Positioning System," Proceedings of the 2013 International Technical Meeting of The Institute of Navigation, San Diego, California, January 2013, pp. 107-111.
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