# Design of a Polarization-Insensitive and Wide-Angle Triple-Band Metamaterial Absorber
## 3 Analysis and Discussion
The reason behind this phenomenon can be better understood through Figure 6b. Only modes one and two are distributed below 10 GHz, and the two modes do not overlap, indicating that the first two absorption bands correspond to one mode, respectively, and the absorption mechanisms are similar, both of which are local resonance modes. Between 10 GHz and 16 GHz, the four modes are concentrated in this  
Figure 5: Wave impedance and equivalent parameters diagram: (**a**) comparison of the real and imaginary parts of impedance; (**b**) comparison of the real parts of the equivalent permittivity and permeability; (**c**) comparison of the imaginary parts of the equivalent permittivity and permeability; (**d**) comparison of the imaginary parts of the equivalent permittivity and permeability. interval and partially overlap, indicating that the absorption in this interval may rely on multilayer interference or other high-frequency effects. Next, the surface current and electric field of MMA at the corresponding absorption frequency were simulated to analyze the absorption mechanism. The electric field polarization direction of the plane wave is set to y direction polarization. The corresponding surface current and electric field diagrams at the three frequency points are shown in Figure 7a-i. First, we will focus on the surface current. As shown in Figure 7a, at 4.23 GHz, the surface current of the upper metal layer is mainly distributed in a ring shape on the outermost structure, while it can be seen in Figure 7d that the current direction of the lower metal layer at 4.23 GHz is opposite to that of the upper metal layer. The currents in the opposite direction on the upper and lower surfaces form a magnetic response. Secondly, we will focus on Figure 7g-i. At 4.23 GHz, the electric field distribution is located in the upper and lower parts of the outermost structure, aligning with the direction of the incident wave's electric field, which is along the y-axis. The vertical electric field is concentrated within the outermost layer of the structure, indicating that electromagnetic resonance occurs in this layer of the MMA. The electromagnetic field and surface current distributions at 7.403 GHz and 14.813 GHz are very similar to those observed at 4.23 GHz, with these  
Figure 6: Refractive index and dispersion diagram: (**a**) refractive index diagram; (**b**) dispersion diagram. distributions located in the middle and innermost layers, respectively. The electromagnetic resonance generated by the metallic structure on the surface of the MMA, along with the magnetic response formed by the opposing circular currents between the upper and lower metal surfaces, enables efficient absorption of electromagnetic waves at specific frequency points. Figure 7: Distribution diagrams of electric fields and surface currents: (**a**) surface current of the upper layer at 4.23 GHz; (**b**) surface current of the upper metal layer at 7.403 GHz; (**c**) surface current of the upper metal layer at 14.813 GHz; (**d**) surface current of the lower metal layer at 4.23 GHz; (**e**) surface current of the lower metal layer at 7.403 GHz; (**f**) surface current of the lower metal layer at 14.813 GHz; (**g**) electric field distribution at 4.23 GHz; (**h**) electric field distribution at 7.403 GHz; (**i**) electric field distribution at 14.813 GHz. The triple-band absorber proposed in this paper can also be analyzed using an equivalent circuit, as shown in Figure 8. From the electric field distribution in Figure 7, it can be observed that, under the influence of the electric field, the electrons in the three-ring structure of the top metasurface undergo directional movement. When excited by electromagnetic waves of different frequencies, each ring can be equivalently modeled as a series connection of an inductor and a capacitor. Additionally, charge accumulation and release occur between adjacent rings within the same subunit, with the equivalent capacitances represented by C4 and C5.