Return Loss And Decoupling Measurements On Antenna Systems

In conjunction with the site infrastructure, the antenna system is a crucial element of mobile base stations and other mobile communications components like repeaters. While the system technology, parameterization and data connection all play an equally important role in determining the quality and availability of a mobile site, the site itself – with its associated infrastructure and antenna system – is very costly to change. If necessary, a defective base station cabinet can be completely replaced. However, this is generally not so easy when it comes to the antenna system and its components.

With its transmit and receive characteristics, the antenna system represents the weakest functional link within the chain of equipment that forms the mobile network's interface to the customer. The antenna system is also exposed to difficult weather conditions. Electrostatic discharges as well as snow, rain and strong temperature fluctuations impose challenging requirements on the materials used. Any water leakage can destroy antennas, cables, filters and antenna amplifiers over a rainy period of only a few weeks, while temperature differences can significantly stress material bonds with different thermal expansion coefficients.

For all of these reasons, antenna systems require special attention. In this educational note, we will first consider some fundamental properties of antennas. We will then discuss the details of various measurements on antenna systems and how to interpret them.