Multiband antenna assembly (10,30) for transmitting or receiving signals in at least two frequency bands (61,62), comprising a monopole antenna with a top substrate (12,32,42) and a base substrate (11,31,51) having defined dimensions and shape, wherein • the top substrate (12,32,42) and the base substrate (11,31,51) are arranged with defined distance relative to each other and define a cavity, wherein a first frequency band (61,62) is basically defined by the dimension of the top substrate (12,32,42), in particular of the top and the base substrate (11,31,51,12,32,42), and in particular by the defined distance, • the top substrate (12,32,42) comprises a set of at least four slots (14a-d,44), wherein a second frequency band (61,62) basically is defined by the design and arrangement of the at least four slots (14a-d,44), the second frequency band (61,62) is different from the first frequency band (61,62), • the cavity is designed so that for the first and the second frequency band (61,62) the monopole antenna has preferred monopole sending and/or receiving directions substantially parallel to the extension of the substrates, in particular horizontally, • the top substrate (12,32,42) is configured to provide a basis for attaching an additional sending and/or receiving unit which provides a preferred sending and/or receiving direction substantially orthogonal to the preferred monopole sending and/or receiving directions, and to provide a ground plane for the additional sending and/or receiving unit, • wherein the set of at least four slots (14a-d,44) are arranged in an adjacent manner so that a size and a shape of the ground plane is defined by the slots, and • the antenna assembly (10,30) comprises a feed configured to transmit signals to and/or from the additional sending and/or receiving unit, wherein the feed is designed as a feeding pin protruding from the base substrate (11,31,51) and extending to the bottom side of the top substrate (12,32,42) in the region of the ground plane, wherein the feeding pin protrudes from the centre of the base substrate (11,31,51) and extends to the centre of the top substrate (12,32,42). • the top substrate (12,32,42) and the base substrate (11,31,51) are arranged with defined distance relative to each other and define a cavity, wherein a first frequency band (61,62) is basically defined by the dimension of the top substrate (12,32,42), in particular of the top and the base substrate (11,31,51,12,32,42), and in particular by the defined distance, • the top substrate (12,32,42) comprises a set of at least four slots (14a-d,44), wherein a second frequency band (61,62) basically is defined by the design and arrangement of the at least four slots (14a-d,44), the second frequency band (61,62) is different from the first frequency band (61,62), • the cavity is designed so that for the first and the second frequency band (61,62) the monopole antenna has preferred monopole sending and/or receiving directions substantially parallel to the extension of the substrates, in particular horizontally, • the top substrate (12,32,42) is configured to provide a basis for attaching an additional sending and/or receiving unit which provides a preferred sending and/or receiving direction substantially orthogonal to the preferred monopole sending and/or receiving directions, and to provide a ground plane for the additional sending and/or receiving unit, • wherein the set of at least four slots (14a-d,44) are arranged in an adjacent manner so that a size and a shape of the ground plane is defined by the slots, and • the antenna assembly (10,30) comprises a feed configured to transmit signals to and/or from the additional sending and/or receiving unit, wherein the feed is designed as a feeding pin protruding from the base substrate (11,31,51) and extending to the bottom side of the top substrate (12,32,42) in the region of the ground plane,