edge 2903 a of the ground plane 2905 a and more precisely substantially close to an end of said short edge 2903 a given that the first radiation booster 2901 a is also located substantially close to said end of the short edge 2903 a the first and second radiation boosters 2901 a 2902 a are arranged near the same corner of the ground plane 2905 a which facilitates the interconnection of the radiation boosters with a radiofrequency system furthermore the second radiation booster 2902 a has undergone a 90 degree clockwise rotation so that the curve delimiting the gap of said second radiation booster 2902 a intersects now the short edge 2903 a of the ground plane 2905 a such an orientation makes it possible for the second radiation booster 2902 a to excite a radiation mode on the ground plane 2905 a having a polarization substantially orthogonal to the polarization of the radiation mode excited on the ground plane 2905 a by the first radiation booster 2901 a orthogonal polarization of the radiation mode refers to the polarization of the radiated electric field such orthogonal polarizations between modes operating in the same frequency band enables a low correlation coefficient which ensures a good mimo performance if the correlation coefficient is high the mimo performance is degraded the advantage of this example is its compactness since both radiation boosters 2901 a and 2902 a are close together even though they are close together the present scheme may achieve a low correlation coefficient since the radiation modes excited by such radiation boosters are substantially orthogonal referring now to fig2 b it is shown another example.