An improved prediction of the wideband beam patterns of an antenna array is proposed based on the active element pattern method and infinitesimal dipole (ID) modeling. In the conventional method, the gain of an antenna array can be easily analyzed. However, the prediction of the shape of the beam pattern is limited due to the usage of the slow-varying assumption and the scaling factor. On the contrary, the proposed method uses the free-space dyadic Green's function, which varies for frequencies and all ID elements. By eliminating the slow-varying assumption and the scaling factor, the proposed method, predicting the shape of the beam pattern of an antenna array, is more accurate than the conventional method. The proposed method was verified by the wideband beam synthesis problem for a seven-patch antenna array.