An antenna device for a radio base station in a mobile cellular telephony network. The device includes a first sub-antenna with a first feed network for distributing signals within the first sub-antenna, and a second sub-antenna with a second feed network for distributing signals within the second sub-antenna. The first and second feed networks are connected to a common main feed network, thus providing the device with a single feed port. A first controller controls one or both of the sub-antennas, and may introduce time delays in signals being transmitted or received by one or both of the sub-antennas. The device may also include a second controller for controlling the common main feed network.