A mutual coupling model for MIMO systems

Wireless communication systems employing multielement antennas (MEAs) are affected by mutual coupling. Accurate and simple models of mutual coupling are essential for better system analysis. In a MEA, mutual coupling depends on the antenna element separation, geometry of array and antenna elements, location of antenna elements in the array, frequency, substrate thickness and constant, near-field scatterers, and direction of arrival (DOA) of the incoming wave. Except near-field scatterers and DOA, the rest of the parameters are fixed for a given MEA system. Since the feeding network for a MIMO system is fixed and most of the mutual coupling is due to surface waves, DOA dependency can be removed for a MIMO mutual coupling model. In this paper, a previously proposed model for mutual coupling is modified to be applicable to MIMO systems. The effect of near-field scatterers on the mutual coupling is specifically investigated to validate the model. Commercially available EM simulators are utilized for this purpose. Once the effect of near-field scatterers is characterized, correlation properties between antenna elements in a MEA can be obtained more accurately and correlation estimation algorithms can be developed accordingly.