Projects:

Definition & Development
of Galileo

Signal Structure

Galileo Test Bed GATE

ESA Galileo Test Bed GSTB_V1

GNSS Software
Simulation

C-Nav Study

Although not considered for the first generation of European Galileo satellites, the (additional) use of C-Band frequencies was topic of a study which was funded by the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt e.V.). A future C-Band signal could use the frequency band between 5010MHz and 5030MHz, thus offering a bandwidth of 20 MHz in a frequency band not yet overloaded by other signal sources.

Application of C-Band navigation signals provides both advantages and drawbacks. At C-Band, the increased free space loss represents the most significant issue. Increased signal attenuation due to foliage attenuation and in case of heavy rain can also be considered as drawbacks. However, small ionospheric effects and technological progress might balance some of the disadvantages from a long term point of view. The main intention of this study was to provide an analysis of the effects of C-Band frequencies on the navigation process.

In order to assess the feasibility of future C-Band technology, the study examined various aspects of signal propagation and satellite signal tracking at C-Band. In order to allow comparison with the current GPS system, the performance expected at C-Band has been compared to the L-Band performance under similar or identical conditions. The results of this analysis were finally discussed with respect to possible consequences for future satellite payload and C-Band receiver design.

Table 1 lists the relevant GPS and Galileo signal parameters. Unless otherwise stated, all computations, diagrams and tables are based on these parameters. Note that in contrast to the discussed GPS ranging codes which consist of rectangular chips, the discussed C-Band signal makes use of the raised cosine pulse shaping scheme (RC)*. The actual shape of a raised cosine chip is defined by the so-called roll-off factor. For the Galileo C-Band signal, a roll-off factor of 0.22 is assumed.

Table 1: GPS and Galileo C-Band signal parameters

* RC pulse shaping schemes have been discussed in 2000/2001; they are currently not part of the Galileo baseline

Signal Propagation and Tracking at C-Band
Impact on Satellite Payload
Impact on Future C-Band Receivers
Conclusions

Point of contact: Markus Irsigler