Comparative study between resonant transmission and extraordinary transmission in truncated periodic arrays of slots

The Method of Moments (MoM) is applied to the determination of the magnetic current density in the slots of a truncated periodic array of slots in a perfect conducting screen. When the array of slots is excited by an impinging plane wave, it is shown that phenomena observed in infinite periodic arrays such as extraordinary transmission and Wood's anomalies start to appear in truncated periodic arrays with roughly 100 (10×10) slots. Also, whereas the magnetic current in the slots under resonant transmission conditions in the truncated case is very similar to that existing in the infinite case except for edge effects, a magnetic current surface wave is excited in the slots under extraordinary transmission conditions in the truncated case. When the center slot of the truncated array is excited by means of a delta-gap generator, whereas a quasi-isotropic magnetic current surface wave is excited at the frequency of resonant transmission, an anisotropic hyperbolic magnetic current surface wave is excited at the frequency of extraordinary transmission.