Design of Metamaterial Impedance Matching Surfaces at Near Field for EMC Solutions

The wave impedance concept is employed in this paper to design an absorber of radiated emissions at a compliance failure frequency. Dimensions of the system box considered in this paper are electrically small at the failure frequency. This result in a complex wave impedance for the radiated emissions at the system box boundary which is in the near field region of the unintentional radiators on the system board. A metamaterial frequency selective absorber is developed to exhibit the target surface impedance for the wave impedance by finding an equivalent bulk material. It is shown that the most effective absorber in near field should conjugate match to the wave impedance at that location. To demonstrate the validity of this approach, the radiated electric fields leaked outside the system box with various material lining its top wall, from copper to the proposed metamaterial design are calculated using full-wave simulations. Obtained results prove that the proposed conjugate matching absorber provides 13.6 dB mitigation of radiated emissions which is 4.7 dB higher than that of a commercial absorber.