On the Mutual Coupling Matrix in Array Signal Processing

We discuss some of the issues associated with the Mutual Coupling Matrix (MCM) which is used extensively to model the antenna array manifold. We show that the MCM does not have the correct structure to provide an accurate mathematical model of the true array manifold. The MCM is not based on physical parameters and this makes it difficult to determine its numerical values for a given antenna array. The MCM is usually treated as an unknown quantity which needs to be estimated. Numerical examples in array processing papers use arbitrary values of the MCM which do not correspond to any physical array. Consequently the observations and conclusions presented in those papers must be treated with some care.