11.4 Radiating Cable Solutions
Radiating cable systems inside tunnels are often to be preferred when compared with antenna distribution in the tunnel; however, in many cases a solution based on distributed Yagi antennas could work just as well and at a much lower cost. The RF environment using radiating cable is much more uniform and easier to plan. The main drawback is the challenge of installation and the price of the installation.
Traditionally, radiating cable is only used for tunnel coverage solutions. However, there are cases where a building has one or several long tunnels, i.e. interconnecting buildings in a campus, long vertical shafts, emergency staircases or elevator shafts, where a radiating cable could be considered as a possible solution.
The typical tunnel application for radiating cable can be seen in Figure 11.6 with a section of tunnel between two underground metro stations. High power remote units installed in the emergency escape tunnels feed the cable sections, and at the stations also the platform antennas. The base station is located at Station B and the optical fiber DAS distributes the signal throughout the tunnels and stations from the central base station.
11.4.1 The Radiating Cable
The radiating cable or ‘leaky feeder’ (as illustrated ...