A Decoupling Technique for Four-Element Symmetric Arrays With Reactively Loaded Dummy Elements

A decoupling technique for a symmetric four-element compact array is proposed. A dummy array terminated with optimum reactive loads is introduced to cancel the mutual couplings between the four radiating elements. A theory that leads to a general design procedure is developed. The technique is demonstrated by three practical design examples, including a compact and low-profile “cheese-cake” antenna array. Calculated channel capacities demonstrate that the performance of a 4-by-4 MIMO communication system that uses the cheese-cake array can be significantly improved as compared to the system using its coupled counterpart. This technique provides a promising approach to the design of a compact four-element array for a MIMO communication system.