An Intuitive Way to Understand Mutual Coupling Effects in Antenna Arrays Using the Poynting Streamline Method

The flow of energy around array antenna in receiving mode can be modeled by generating streamlines of the Poynting vector field. From the streamlines that terminate on the array element loads, a geometrical shape can be assigned to the effective area of the array. These concepts provide an intuitive tool for understanding mutual coupling effects in antenna arrays. The decrease in directivity associated with mutual coupling effects, the so-called element-gain paradox, can be explained by the overlap of the element effective area shapes. The critical element spacing for the element-gain paradox effect can be predicted from the effective area shape for a single isolated array element. Antenna design for minimizing mutual coupling, which is of interest in multiple input multiple output communications systems, magnetic resonance imaging arrays, astronomical arrays, and other applications, can be guided by analysing the effective area shape for a single isolated array element.