Fig. 1. Electromagnetic parameter test sample.(a) Graphene composite wire; (b) coaxial ring

Fig. 2. Schematic diagram of pyramid structure. (a) Incident direction of electromagnetic waves; (b) periodic arrangement; (c) unit cross-sectional size; (d) horizontal gradient distribution; (e) stereo gradient distribution; (f) stereo gradient distribution wireframe

Fig. 3. Physical picture of C10 pyramid absorber printed sample

Fig. 4. Electromagnetic parameters of composite wire. (a) Real part of complex permittivity ε´; (b) imaginary part of complex permittivity ε"; (c) real part of complex permeability μ´; (d) imaginary part complex permeability μ"

Fig. 5. Impedance matching characteristics of absorber

Fig. 6. Curves of reflection losses of absorbers C1-C5

Fig. 7. Energy loss distribution of horizontally distributed absorber at different frequencies. (a) 2 GHz; (b) 10 GHz; (c) 18 GHz

Fig. 8. Reflection loss curves of different absorber combinations. (a) C6-C9 (horizontal distribution); (b) C10-C13 (three-dimensional distribution)

Fig. 9. Reflection loss of absorber under different distribution modes of absorber

Fig. 10. Energy loss at resonance frequency of absorber with different distribution modes. (a) Horizontal distribution 12.6 GHz; (b) stereo distribution 17.4 GHz

Fig. 11. Electric field distribution diagram at resonant frequency (17.4 GHz). (a) Electric field diagram of top section; (b) electric field diagram of front section

Fig. 12. Magnetic field distribution diagram at resonant frequency (17.4 GHz). (a) Magnetic field diagram of top section; (b) magnetic field diagram of front section

Fig. 13. Propagation of electromagnetic waves

Fig. 14. Comparison curves between simulation and measured results of reflection loss of absorber