Near-field superdirectivity for coupled dimers of meta-atoms

We present new results relating far-field and near-field superdirectivity for a dimer endfire array in which only one of the meta-atoms is excited. We deduce conditions for achieving superdirectivity in terms of structure parameters (distances between meta-atoms, their quality factors and the values of mutual coupling) and show that the required sets of parameters are different for far-field and near-field superdirectivity. Our results are relevant to medical imaging applications such as MRI and associated technologies.