Table 1. Comparison of absorption properties of the planar MMAs reported in literatures and this work proposed here.

Feature of MMAs	Absorption waveband	Thickness	Wob/t	Reference
Truncated pyramidal	7.8–14.7 GHz	5 mm	3.61	27
Double-corrugated structure	7.8–16 GHz	5 mm	3.94	28
1-layer donut-shape	5.03–5.13 GHz	0.8 mm	1.45	41
3-layer crosses structure	4.45–4.95 THz	3.8 μm	1.79	17
Double-layered grating	0.25–2.5 THz	620 μm	1.74	45
Saw-toothed multi-layer slab	0.3–4.7 μm	1 μm	4.40	10
Multiple-layer pyramidal	1–14 μm	3 μm	4.33	30
Hyperbolic waveguide taper array	2.9–5 μm	40 μm	5.00	33
Multi-sized sow-wave hyperbolic	0.5–2.5 μm	56 μm	3.75	34
Truncated pyramidal	0.2–5.8 μm	56 μm	1.00	35
1-layer mixed-size square hole	583–613 nm	15 μm	0.20	14
Multi-sized Pyramidal using TM210	7–18 GHz	4.36 mm	6.01	This work