1. Field of the Invention
The present invention relates to an onboard information system having an antenna for receiving satellite-based geoposition data.
2. Description of the Related Art
Onboard information systems, particularly tachographs, toll collection appliances or what are known as universal onboard units, which combine the functions of tachographs and toll collection appliances, must meet ever higher technical demands. Particularly the possibility of tracking the position of a vehicle, for example a heavy goods vehicle, using a geoposition system affords a large number of new opportunities for application, for toll collection, navigation or monitoring of safety-related goods during transport.
EP 1 328 041 A1 discloses a receiver arranged in a toll computer for data from the global positioning system (GPS. A drawback of the prior art is that although a receiver module for geoposition data may be integrated in a housing for a toll collection system, the associated antenna is fitted outside of the housing at another position in the vehicle. This fitting in the vicinity of a screen or outside of the vehicle interior is necessary because signals from geoposition satellites are much weaker in comparison with mobile radio signals. By way of example, mobile radio signals based on the GSM standard have a signal strength of between 3 dB and −6 dB, whereas signals from geoposition satellites have a signal strength of between −140 dB and −160 dB on the Earth's surface. On account of the weak geoposition signals, it is often even necessary for an antenna to be fitted on an outer side of the vehicle, and hence for there to be a direct line of sight between the antenna and the sending satellites. This is particularly disadvantageous because beside mounting of the antenna this requires an additional wired or wireless connection to be made between the antenna and the receiver module accommodated in the housing of the onboard information system.