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GNSS Over China: The Compass MEO Satellite Codes

Compass M-1 launch.jpgCompass M-1 Launch, April 14, 2007
With the launch of its first middle-earth-orbiting (MEO) Compass satellite, China has put forth its GNSS entry. The key to using and understanding the performance of the Compass M-1 navigation signals is revealed by its spread spectrum code. This article by a team of Stanford University researchers presents the spread spectrum codes being broadcast by this satellite.

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On April 14, 2007 (local time), China launched the Compass M-1 satellite. This satellite represents the first of a new global navigation satellite system (GNSS) that is planned to have a total of 35 satellites. Unlike prior Chinese navigation satellites, Compass M-1 broadcasts in L-band, using signal structures similar to other GNSS systems and sharing frequencies near to or overlapping those of GPS, Galileo, and GLONASS.

The addition of another GNSS, particularly one that will broadcast in the same frequency bands as GPS and Galileo, both excites and intrigues the GNSS community. Such a system has the potential to introduce benefits – as well as concerns – for GNSS users. Numerous researchers around the world, including Stanford University (SU), have been interested in examining the navigation signal of this system.

To understand its effects and to develop receivers that can track the signal, one must understand the signal structure being used. In the case of Compass, this means determining and understanding its spread spectrum codes. This article will present the Compass codes and provide an overview of how our team at Stanford determined these.

(For the rest of this story, please download the complete article using the PDF link above.)


Stanford University researchers use an Agilent 89600 vector signal analyzer from Agilent Technologies, Palo Alto, California, USA, to collect signals received at the SGMS. The skyplot in Figure 1 was generated with satellite tracking software, Nova for Windows, developed by Northern Lights Software Associates, Jamesville, New York, USA.

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