Fig. 4
a and c show the |E| field distributions of the frequency points E and F of the unperforated rectangular resonator, respectively. b and d provide the |Hy| field distributions of the frequency points E and F of the unperforated rectangular resonator, respectively. e, g, i, and (k) show the |E| field distributions of the frequency points A, B, C, and D of the perforated rectangular resonator, respectively. f, h, j, and l give the |Hy| field distributions of the frequency points A, B, C, and D of the perforated rectangular resonator, respectively