"An electrically conductive, transparent layer made from metals or metal oxides is applied to the window panes. Along lines in a special structure, lasers are used to vaporize the pane's metallic coating. This allows radio signals in certain frequency ranges to pass through unhindered, while radio signals with other frequencies are attenuated. This approach leads to a massive improvement in the receiving level for mobile terminal devices in the train," explains Lukas W. Mayer, project manager at Siemens. Previous solutions had the disadvantage that they were only really effective in a narrow frequency range, while in other ranges the transmission loss via the window panes was made even worse. With our solution, equipping a high-speed train carriage with a high-frequency window pane reduces the shielding to such an extent that the signal strength in mobile radio bands is 50 times greater. Measurements conducted with a modified ÖBB Railjet have shown that the time window in which good 4G reception is available increases by 33 percent," says Mayer.
"We wanted a cost-effective solution for our customers," stresses Mehrdad Madjdi from the Siemens Mobility Division, and goes on to detail the benefits: "The window panes can be used for decades without the need for maintenance. They may be more expensive to buy, but they generate significant savings in the long term compared to in-train repeaters." This is due to the low transmission loss of the window panes across a broad frequency range from 700 megahertz to 3.5 gigahertz. The advantage lies in the fact that the window panes are suitable not just for today's frequency bands but also for future mobility standards. This means that the latest mobile services are available to passengers immediately without the need for any further investment. Installation, too, is cost-effective: no additional technical components are needed to fit the new panes into the train, and the technicians require no special qualifications. Existing carriages can of course be retrofitted at any time with the window panes.
Initial passenger trials have shown that the structure is almost invisible to the naked eye. Those taking part in the trials were unable to detect any reduction in visibility during the day or at night. In some cases, the coating can even result in better energy efficiency, which in turn enhances passenger comfort. The verdict: greater convenience and better travel quality. The innovative window panes will be used for the first time in regular passenger operation from the end of 2018 on the trains of the Rhein-Ruhr-Express (RRX) in Germany.