In Coherent MIMO phased array, different codes are transmitted at the same time by the different antenna elements (or subarray). Compared to classical transmission (linear phase law on the array antenna to focus the beam in one direction), MIMO transmission is very stressful for the array because of random like phase between adjacent elements and even in some cases opposite phase between adjacent elements. In this context, the paper present a general frame to describe coupling effect in MIMO Phased array, involving a circuit modeling of the antenna array and exploiting mutual impedances between antenna elements. Illustrations are provided with exact simulation of a dipole array.