Abstract: An active antenna array is arranged to activate subsets of switchable elements causing the antenna to form a first beam having a first beam pattern, and later to form a second beam having a second beam pattern of substantially identical far field radiation pattern to the first beam pattern but with different origins. A receiver receives radiation reflected from a target back to the antenna when the antenna is configured with the first beam pattern and then when configured with the second beam pattern, and compares 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. A target locating means determines the angular location of the target from the phase difference signal.

Abstract: An active antenna array is arranged to activate subsets of switchable elements causing the antenna to form a first beam having a first beam pattern, and later to form a second beam having a second beam pattern of substantially identical far field radiation pattern to the first beam pattern but with different origins. A receiver receives radiation reflected from a target back to the antenna when the antenna is configured with the first beam pattern and then when configured with the second beam pattern, and compares 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. A target locating means determines the angular location of the target from the phase difference signal.