The methods for managing access to a communication medium shared by a plurality of radio communication devices. By controlling the interference of the electromagnetic fields radiated by the near-field plate with that of a source, the near-field plate can form a subwavelength near-field pattern in a forward direction, while suppressing fields in other directions, such as those reflected. Also, there is a problem of warping the substrate by a difference in thermal expansion coefficients between the substrate and the nitride thin film.