Phased-Mode Spoof Surface Plasmon Polaritons Antenna

Harrington has proved that the maximum directivity coefficient D of a source region is a function of the number of multipole modes N (Dmax = N2 + 2N) (Harrington in IRE Trans. Antennas Propag. 6:219, 1958; Harrington in J. Res. Natl. Bur. Stand. 64D:1, 1960). Theoretically, the larger the N is, the larger the directional coefficient D is, and the stronger the super directional needle radiation is. When the electric and magnetic dipoles are excited with equal amplitude and equal phase, the pattern is the heart shape in the electric and magnetic fields. The forward radiation is enhanced and the backward radiation is obviously suppressed. This structure is often called Huygens source. This kind of magnetoelectric orthogonal radiation element can obtain higher directional radiation gain. On the one hand, it preliminarily proves the correctness of Harritung’s theory. On the other hand, it also shows that multiple modes can share the same aperture, and multiple modes can be superimposed with each other to form a comprehensive mode with shared aperture.