An RF antenna system (100, 1014, 1014') configured for transmitting RF excitation signals into and/or for receiving MR signals from an MR imaging system's (1000, 1100, 1200) imaging volume, wherein the RF antenna system comprises: - a coil former (100, 1014, 1014') adjacent to the imaging volume; and - a resonator (400, 500, 600) attached to the coil former and tuned to at least one resonant frequency and formed from electrical connections between multiple capacitors, wherein the multiple capacitors are distributed in a two-dimensional periodic pattern (300, 700, 800, 900) about and along the coil former, wherein the periodic pattern of capacitors forms a structure that is configured to behave as a two-dimensional dielectric conductor, wherein the coil former is formed from a dielectric, wherein the coil former comprises a first surface and a second surface, wherein each of the multiple capacitors is formed by a first conductive portion and a second conductive portion, wherein the first conductive portion is attached to the first surface, wherein the second conductive portion is attached to the second surface, wherein each capacitor is formed from a respective portion of the coil former with the first conductive portion and the second conductive portion, characterised in that the periodic pattern is divided into electrically isolated groups, wherein each of the electrically isolated groups is electrically isolated from any other of the electrically isolated groups, and wherein each of the electrically isolated groups is configured to be connected to a separate radio-frequency channel. - a coil former (100, 1014, 1014') adjacent to the imaging volume; and - a resonator (400, 500, 600) attached to the coil former and tuned to at least one resonant frequency and formed from electrical connections between multiple capacitors, wherein the multiple capacitors are distributed in a two-dimensional periodic pattern (300, 700, 800, 900) about and along the coil former, wherein the periodic pattern of capacitors forms a structure that is configured to behave as a two-dimensional dielectric conductor, wherein the coil former is formed from a dielectric, wherein the coil former comprises a first surface and a second surface, wherein each of the multiple capacitors is formed by a first conductive portion and a second conductive portion, wherein the first conductive portion is attached to the first surface, wherein the second conductive portion is attached to the second surface, wherein each capacitor is formed from a respective portion of the coil former with the first conductive portion and the second conductive portion, characterised in that the periodic pattern is divided into electrically isolated groups, wherein each of the electrically isolated groups is electrically isolated from any other of the electrically isolated groups, and wherein each of the electrically isolated groups is configured to be connected to a separate radio-frequency channel. each of the multiple capacitors is formed by a first conductive portion and a second conductive portion, wherein the first conductive portion is attached to the first surface, wherein the second conductive portion is attached to the second surface, wherein each capacitor is formed from a respective portion of the coil former with the first conductive portion and the second conductive portion, characterised in that the periodic pattern is divided into electrically isolated groups, wherein each of the electrically isolated groups is electrically isolated from any other of the electrically isolated groups, and wherein each of the electrically isolated groups is configured to be connected to a separate radio-frequency channel.