Fig 1.
Metamaterial joint T-D geometry, equivalent circuit and fabrication.
(a) Proposed metamaterial unit cell structure, (b) equivalent circuit [19], (c) Flexible Nickel aluminate material (NiAl2O4); fabricated proposed design on (d) FR-4 substrate and (e) 2×2 array prototype on flexible NiAl2O4 substrate.
Table 1.
Design parameter of the proposed flexible metamaterial structure.
Fig 2.
Measurement set-up of the proposed flexible metamaterial structure.
Fig 3.
Simulation set-up with simulated and experimental results.
(a) The geometry of the proposed structure in z-axis wave propagation, (b) Simulated reflection and transmission coefficients in CST, (c) Simulated reflection and transmission coefficients in HFSS, (d) The measured and simulated comparative result, (e) Amplitude of Effective parameters, (f) Results of 13 × 18 mm2 unit cell array refraction and transmission coefficient.
Fig 4.
Surface current distribution at (a) 6.60 GHz, (b) 9.16 GHz, (c) 17.28 GHz and (d) 11.35 GHz.
Fig 5.
Design of metamaterial unit cell.
(a) Proposed structure (b) modified structure 1 (c) modified structure 2 (d) modified structure 3.
Table 2.
Summary of resonance points of proposed and modified metamaterial structures.
Fig 6.
Resonance frequency points of proposed, MS1, MS2 and for MS3 metamaterial structures.
Fig 7.
E-fields for (a) proposed structure at 9.32 GHz (b) MS1 at 16.68 GHz (c) MS2 at 7.98 GHz (d) MS3 at 10.95 GHz and H-fields for (e) proposed structure at 9.32 GHz (f) MS1 at 16.68 GHz (g) MS2 at 7.98 GHz (h) MS3 at 10.95 GHz.
Fig 8.
Metamaterial characterization at (a) the geometry for y axis wave propagation, (b) the simulated refraction and transmission coefficient, (c) amplitude of effective parameters.
Table 3.
Performance of the proposed metamaterial in the z- and y-direction wave propagation.
Fig 9.
Simulated transmission coefficient at the thickness of 0.50 mm, 0.76 mm, 1.00 mm, 1.20 mm, 1.40 mm, 1.60 mm and 1.60 mm in, (a) C-band, (c) X-band, (e) Ku-band simulated by CST Microwave studio software and (b) C-band, (d) X-band, and (f) Ku-band simulated by HFSS software.
Fig 10.
Simulated effective parameters.
(a) permittivity (b) permeability and (c) refractive index at the thickness of 0.50 mm, 0.76 mm, 1.00 mm, 1.20 mm, 1.40 mm, 1.60 mm and 1.60 mm.
Table 4.
Thickness variation effects on the resonance frequency for proposed metamaterial.
Fig 11.
Simulation set-up and experimental results.
(a) The geometry for z-axis wave propagation, (b) Reflection and transmission coefficients simulated by CST and HFSS electromagnetic simulator, (c) Measured and simulated transmission coefficients, (d) Amplitude of the effective parameters.
Fig 12.
Surface current distribution at (a) 6.85 GHz, (b) 10.18 GHz, (c) 16.17 GHz and (d) 12.09 GHz.
Fig 13.
Metamaterial characterization at (a) the geometry at y-axis wave propagation, (b) simulated transmission coefficient, (c) effective permittivity, permeability and refractive index parameters.
Table 5.
Performance of the proposed metamaterial in the z- and y-direction wave propagation.
Fig 14.
Simulated transmission coefficients at the thickness of 0.50 mm, 0.76 mm, 1.00 mm, 1.20 mm, 1.40 mm, 1.60 mm and 1.60 mm in, (a) C-band, (c) X-band, (e) Ku-band simulated by CST Microwave studio software and (b) C-band, (d) X-band, and (f) Ku-band simulated by HFSS software.
Fig 15.
Simulated effective parameters at the thickness of 0.50 mm, 0.76 mm, 1.00 mm, 1.20 mm, 1.40 mm, 1.60 mm and 1.60 mm are, (a) permittivity, (b) permeability and (c) refractive index.
Table 6.
Thickness variation effect on resonance frequency for proposed metamaterial structure.
Fig 16.
The resonance frequencies are changing with different substrate thickness at (a) C-band (b) X-band (c) Ku-band.
Table 7.
Comparing the experimental results of the proposed structure to the previous work.