MIMO antenna modules and antenna units for a wireless communication system are provided. In one embodiment, a remote unit comprises: a controller module, comprising: a first substrate having a first ground plane, control circuitry and interface circuitry on the first substrate, a first connection region formed in the first substrate; and at least one antenna module coupled to the controller module, the antenna module comprising: a second substrate having a second ground plane, antennas on the second substrate, a second connection region on the second substrate and coupled to the interface circuitry via the first connection region, wherein the second connection region communicates data between the interface circuitry and the antennas, and a set of ground-plane contacts on the second substrate that electrically couple the first ground plane to the second ground plane of the second substrate when the second connector region is engaged with the first connector region.