Figure 23: Some of the most common DGS structures employed in the applications [78]. (a) Dumbbell-shaped, (b) circular head dumbbell, (c) arrow head dumbbell, (d) U-shaped, (e) H-shaped, (f) squared heads connected with U-slots, (g) squared slots connected with narrow slot at edge, (h) cross-shaped, (i) interdigital, (j) fractal, (k) open loop dumbbell, (l) L-shaped, (m) meander lines, (n) U-head dumbbell, (o) double equilateral U, (p) V-shaped, (q) split-ring resonators, (r) concentric ring shaped, (s) half-circle, and (t) spiral-shaped.