Diversity aerials ensure the best reception quality even when the available radio signal is poor. High-rise buildings and hills reflect the electromagnetic waves from radio and television transmitters. For this reason, an aerial receives not just one signal, but also staggered signal reflections, which may impair reception quality. This is referred to as multi-path interference. With the Diversity Aerial system, the radio signal is received by more than one aerial (up to four) and the receiver filters out the signal interference by intelligently combining the signals from the different aerials.
Article source: www.volkswagen.co.uk