An improved active antenna system is distinguished inter alia by the following features: comprising a first antenna group (5) which is provided for transmitting and receiving operation, comprising a second antenna group (10) which is provided for receiving operation, the two antenna groups (5, 10) are arranged above one another, and the supply network (N11, N12) of the first antenna group (5) has an amplitude distribution which is frequency-dependent, i.e. dependent on a transmitting and a receiving frequency.