This paper describes an extension of a radar traffic data acquisition sensor. The extension enables the sensor to establish a unidirectional short range broadband communication link between the sensor and vehicles, passing below it. A possible application of the radar-communication system is within the field of dynamic traffic management. The centre frequency of the link is within the 61 GHz ISM band. This choice of frequency may be favourable regarding the frequency availability all over Europe and the demand for unified links. The message is organized in telegrams each consisting of a fixed synchronization preamble of 64 bits and an occasionally updated data part. The data rate may be up to 10 Mbit/s. The total amount of data transmitted into the car depends on the specification of the link and the service and may exceed 50,000 bits at a vehicle speed of 200 km/h concerning a 3 x 13 degree directive antenna at the beacon side. With the test equipment used no channel coding was necessary to provide error free data reception. Nevertheless forward error correction may be advantageous with regard to attenuation due to windscreens and heavy weather conditions and with regard to an equivalent isotropic radiated power (EIRP) of less than 32 dBm. Considering only the communication link theoretically almost any modulation scheme is possible. Regarding the radar functions and low cost receiver structures nowadays subband modulation based on ASK seems to be best suited. Structures enabling monolithic integration of the 61 GHz components are proposed.
Samenvatting