Filtering Antenna Synthesis Based on Characteristic Mode Theory

This article developed a topology synthesis method based on characteristic mode theory (CMT) for the design of filtering antenna. The realization mechanism of radiation nulls of the antenna has been revisited and related to the characteristic fields and characteristic currents in the CMT. Two kinds of the methods based on the characteristic fields and the characteristic currents have been proposed to design the filtering antennas. Combined with the nondominated sorting genetic algorithm-II (NSGA-II), a CMT-based optimization procedure for the topology structure has been presented. With the proposed optimization algorithm, two filtering antennas without and with the consideration of the feeding port are designed, respectively, to achieve the radiation nulls at lower and upper band edges. For demonstration, the two proposed filtering antennas have been fabricated and measured. Good agreement between the simulated and measured results is observed to show the effectiveness of the proposed optimization design method for the topology structures with the filtering responses.