The present disclosure relates to a sub-array antenna (101a, 101b, 101c) adapted to be mounted to at least one other sub-array antenna (101a, 101b, 101c) along at least one extension (E1, E2) to form an array antenna (100). The sub-array antenna (101a, 101b, 101c) comprises a conductive
ground plane (102a, 102b, 102c) and at least one edge portion (104a, 105a; 104b, 105b; 104c, 105c) adapted to face the edge portion of an adjacent sub-array antenna. The edge portions (104a, 105a; 104b, 105b; 104c, 105c) at least partially include a locking structure, the locking structure including an outer locking portion (103a, 103b) and a recess (106a, 106b) located between the outer locking portion (103a, 103b) and the
ground plane (102a, 102b, 102c) in the direction of extension (E1, E2). The recess (106a, 106b) is adapted to receive an adjacent outer locking portion (103b, 103a) of an adjacent sub-array antenna (101b, 101a), and the outer locking portion (103b, 103a) is adapted to engage the recess (106b, 106a) of the adjacent sub-array antenna (101b, 101a). The outer locking portion (103b, 103a) and the recess (106a, 106b) are conductive and electrically connected to the
ground plane (102a, 102b).