An active antenna array of the kind comprising a plurality of switchable antenna elements controlled by a switching means which is operable to selectively activate selected ones of the antenna elements to emit/receive a shaped beam of radiation, the apparatus is arranged in use to produce a plurality of pairs of first and second drive signals, in which for each pair the first drive signal causes the switching means to activate a first subset of elements at a first period of time, the first subset of elements causing the antenna to form a first beam having a first beam pattern, and the second drive signal causes the switching means to activate a second subset of the elements at a second period of time which is different from the first period of time, the second subset of elements causing the antenna to form a second beam having a second beam pattern, the first and second beam patterns of each pair comprising substantially identical far field radiation patterns but with different origins which are offset along an axis defined relative to the antenna array by a predetermined amount, and further comprising: a receiver which receives radiation that has been emitted by the antenna and subsequently reflected from a target back to the antenna when the antenna is configured with the first beam pattern and receives radiation that has been emitted by the antenna and subsequently reflected from a target back to the antenna when the antenna has been configured with the second beam pattern, a comparison means for comparing, for each pair of first and second drive signals, the phase of the radiation received at the receiver when the antenna is configured with the first beam pattern with the phase of the radiation received at the receiver when the antenna is configured with the second beam pattern to provide a phase difference signal, and target locating means which determines the angular location of the target relative to the antenna by processing each phase difference signal with the known offset between the different origins of the first and second far field radiation patterns corresponding to the respective pair of signals, and in which the beam shapes processed by the first and second drive signals for each pair are different from each of the other pairs so that each pair of first and second drive signals provides a different directional sensitivity. a receiver which receives radiation that has been emitted by the antenna and subsequently reflected from a target back to the antenna when the antenna is configured with the first beam pattern and receives radiation that has been emitted by the antenna and subsequently reflected from a target back to the antenna when the antenna has been configured with the second beam pattern, a comparison means for comparing, for each pair of first and second drive signals, the phase of the radiation received at the receiver when the antenna is configured with the first beam pattern with the phase of the radiation received at the receiver when the antenna is configured with the second beam pattern to provide a phase difference signal, and target locating means which determines the angular location of the target relative to the antenna by processing each phase difference signal with the known offset between the different origins of the first and second far field radiation patterns corresponding to the respective pair of signals, and in which the beam shapes processed by the first and second drive signals for each pair are different from each of the other pairs so that each pair of first and second drive signals provides a different directional sensitivity. <EOS>