An electromagnetic reactive edge treatment including an array of capacitively-loaded loops is disposed at or near an edge of a conductive wedge. The axes of the loops are oriented parallel to the edge of the wedge. This edge treatment may enhance or suppress the hard diffraction coefficient, depending on the resonant frequency fo of the array of loaded loops. Diffraction of incident waves that are lower (higher) in frequency than fo may be enhanced (suppressed) due to the increase (decrease) in effective permeability of the volume occupied by the array of loops. Applications include controlling antenna patterns, side lobe levels, and backlobe levels for antennas mounted on conductive surfaces near edges or corners.