Mutual coupling in MIMO wireless systems: a rigorous network theory analysis
IEEE Transactions on Wireless Communications
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A practical method for decoupling small-form two- and four-element antenna arrays is discussed. This method is generic in the sense that it works on any types of antenna elements as long as they are identical and symmetrically arranged. The basic principle is to use a passive multi-port network to separate out various orthogonal radiation modes of a highly-coupled array for transmission and reception. In other words, the array as a whole, rather than each element, is treated as a single radiation entity. As these mutually orthogonal modes are uncorrelated and have no real energy exchange among them, the network ports associated with these modes are well isolated from each other. Therefore, problems on impedance matching and signal correlation due to close spacing of elements in traditional compact arrays can be avoided. Experimental arrays of fourelement with around 0.1λ element-to-element separation have been fabricated and tested to demonstrate the practicability of the idea. Measurement results are in good agreement with expectations, showing promising potential of the proposed approach for miniaturized arrays in handheld terminals.