A metamaterial-based insulator is proposed for highly compact MIMO-systems. In previous work, the proposed insulator has been demonstrated to reduce efficiently the coupling at PEC boundaries between two very close antennas on a common ground plane. The present study concentrates on the effects of this insulator on the antenna radiation pattern. The chosen operating frequency is 2.4 GHz considering that it is a usual frequency for many indoor wireless applications. The theoretical results are supported by numerical simulations.