In a further possible implementation form of the first aspect, the first wall comprises at least one first recess, the second wall comprises at least one second recess at least partially aligned with the first recess, and the first recess and the second recess extending perpendicular to a longitudinal extension of the groove, allowing the printed circuit board to be part of the antenna arrays and facilitating use of dual polarization radiation beams. Electromagnetic isolation between adjacent antenna elements of the antenna arrays is achieved by the first recess and the second recess, thus further improving the efficiency of the antenna arrays.

In a further possible implementation form of the first aspect, the first antenna array comprises at least one first antenna element, the first antenna element comprising a waveguide and a first signal feeding connection, the waveguide being formed by the first wall, the second wall, the connecting surface, the first surface of the conductive component, and the second surface of the conductive component, the first signal feeding connection being coupled to the first wall, providing an antenna array which is constructed mainly of other preexisting components and which requires as few additional components as possible. For example, the disclosed antenna elements require only λ/20 of extra space between the first wall and the second wall.