Millimetre-wave propagation along railway lines

The operation of modern railway systems requires a high degree of safety and reliability. This can be accomplished by using millimetre waves for communication and control. Besides high-data-rate relaying, this approach enables the transmission of highly concentrated radio beams; thus a `radio tube¿¿ can be shaped and limited to the railway track only. There are two frequency ranges of interest: the atmospheric window around 35 GHz and the attenuation peak at 60 GHz. Propagation measurements at both frequencies have been carried out along different railway lines in co-operation with the Deutsche Bundesbahn: the German Federal railway authority. The various influences of the railway environment have been investigated thoroughly. These measurements are described in detail.