A radar system (101, 2101, 400, 800) comprising a first and a second antenna module (110a, 2110a, 410a, 810a), (110b, 2110b, 410b, 810b), each said antenna module comprising: a first planar slotted waveguide antenna array (111a, 2111a, 400aa, 800aa), (111b, 2111b, 400ab, 800ab) configured for radiating electromagnetic waves (113a, 2113a), (113b, 2113b); and a second planar slotted waveguide antenna array (112a, 2112a, 400ba, 800ba), (112b, 2112b, 400bb, 800bb) configured for receiving electromagnetic waves; wherein for each of the antenna modules, each planar slotted waveguide antenna array comprises several longitudinal extending waveguide columns (203, 303a, 303b, 403aa,ab,ba, bb) disposed in a parallel and adjacent position with respect to one another, said waveguide columns having a front side and a rear side with a plurality of cavity slots on the front side, and said waveguide columns further having first and second column ends; and wherein for each of the antenna modules, the first and second antenna arrays are arranged with the longitudinal direction of the waveguide columns extending in a single, horizontal direction, and with the waveguide columns of the first antenna array (111a, 2111a, 400aa, 800aa), (111b, 2111b, 400ab, 800b) disposed in a parallel position to the waveguide columns of the second antenna array (112a, 2112a, 400ba, 800ba), (112b, 2112b, 400bb, 800bb); said radar system further comprising a rotation system (116, 2116, 416) configured for supporting and rotating the first and second antenna modules around a vertical axis (115, 2115), with the first and second antenna modules arranged in a back-to-back position on opposite sides of a plane intersecting the vertical axis of rotation, and with the rear side of the waveguide columns of the antenna arrays of the first antenna module facing the rear side of the waveguide columns of the antenna arrays of the second antenna module; characterized in that for each antenna module, the waveguide columns of the first antenna array (111a, 2111a, 400aa, 800aa), (111b, 2111b, 400ab, 800ab) are disposed below the waveguide columns of the second antenna array (112a, 2112a, 400ba, 800ba), (112b, 2112b, 400bb, 800bb) when compared to the vertical axis of rotation (115, 2115); and in that for each antenna module, an electromagnetic shield or shield plate (120a, 2120a, 2121a, 420a, 820a, 821a), (120b, 2120b, 2121b, 420b, 820b, 821b) is arranged substantially parallel to the waveguide columns and between the first lower radiating antenna array and the second upper receiving antenna array, said shield or shield plate extending outwards from the front side of the antenna module. a first planar slotted waveguide antenna array (111a, 2111a, 400aa, 800aa), (111b, 2111b, 400ab, 800ab) configured for radiating electromagnetic waves (113a, 2113a), (113b, 2113b); and a second planar slotted waveguide antenna array (112a, 2112a, 400ba, 800ba), (112b, 2112b, 400bb, 800bb) configured for receiving electromagnetic waves; wherein for each of the antenna modules, each planar slotted waveguide antenna array comprises several longitudinal extending waveguide columns (203, 303a, 303b, 403aa,ab,ba, bb) disposed in a parallel and adjacent position with respect to one another, said waveguide columns having a front side and a rear side with a plurality of cavity slots on the front side, and said waveguide columns further having first and second column ends; and wherein for each of the antenna modules, the first and second antenna arrays are arranged with the longitudinal direction of the waveguide columns extending in a single, horizontal direction, and with the waveguide columns of the first antenna array (111a, 2111a, 400aa, 800aa), (111b, 2111b, 400ab, 800b) disposed in a parallel position to the waveguide columns of the second antenna array (112a, 2112a, 400ba, 800ba), (112b, 2112b, 400bb, 800bb); said radar system further comprising a rotation system (116, 2116, 416) configured for supporting and rotating the first and second antenna modules around a vertical axis (115, 2115), with the first and second antenna modules arranged in a back-to-back position on opposite sides of a plane intersecting the vertical axis of rotation, and with the rear side of the waveguide columns of the antenna arrays of the first antenna module facing the rear side of the waveguide columns of the antenna arrays of the second antenna module; characterized in that for each antenna module, the waveguide columns of the first antenna array (111a, 2111a, 400aa, 800aa), (111b, 2111b, 400ab, 800ab) are disposed below the waveguide columns of the second antenna array (112a, 2112a, 400ba, 800ba), (112b, 2112b, 400bb, 800bb) when compared to the vertical axis of rotation (115, 2115); and in that for each antenna module, an electromagnetic shield or shield plate (120a, 2120a, 2121a, 420a, 820a, 821a), (120b, 2120b, 2121b, 420b, 820b, 821b) is arranged substantially parallel to the waveguide columns and between the first lower radiating antenna array and the second upper receiving antenna array, said shield or shield plate extending outwards from the front side of the antenna module.