Author Contributions
Conceptualization, C.C., C.P., A.G. and C.M.; methodology, C.C., A.G. and C.P.; validation, C.C., A.G., C.P., M.G. and S.A.; formal analysis, C.C.; investigation, C.C., C.P., A.G. and C.M.; resources, S.A. and M.G.; data curation, C.C., C.P., A.G. and C.M.; writing—original draft preparation, C.C.; writing—review and editing, C.C., A.G. and C.P.; visualization, S.A. and M.G.; supervision, C.M.; project administration, C.C.; funding acquisition, C.C. All authors have read and agreed to the published version of the manuscript.
Figure 1.
The dimensions of the initial antenna structure: (a) modeled with HFSS; (b) constructed on an FR4 epoxy dielectric.
Figure 1.
The dimensions of the initial antenna structure: (a) modeled with HFSS; (b) constructed on an FR4 epoxy dielectric.
Figure 2.
The PCB production line LPFK.
Figure 2.
The PCB production line LPFK.
Figure 3.
Experimental stand for the measurements of the S parameters with nanoVNA SAA-2N.
Figure 3.
Experimental stand for the measurements of the S parameters with nanoVNA SAA-2N.
Figure 4.
S11 values obtained for the initial structure: (a) measured; (b) obtained through numerical analysis.
Figure 4.
S11 values obtained for the initial structure: (a) measured; (b) obtained through numerical analysis.
Figure 5.
Gain of the initial structure.
Figure 5.
Gain of the initial structure.
Figure 6.
Diagram of the optimization process for the planar Yagi Uda antenna analyzed.
Figure 6.
Diagram of the optimization process for the planar Yagi Uda antenna analyzed.
Figure 7.
S11 values obtained for the structure with different dielectrics with thicknesses: (a) 0.51 mm; (b) 1.51 mm.
Figure 7.
S11 values obtained for the structure with different dielectrics with thicknesses: (a) 0.51 mm; (b) 1.51 mm.
Figure 8.
S11 values obtained for the structure with different dielectric thicknesses for: (a) FR4; (b) RO3003; (c) RO4003C; (b) RO4350B.
Figure 8.
S11 values obtained for the structure with different dielectric thicknesses for: (a) FR4; (b) RO3003; (c) RO4003C; (b) RO4350B.
Figure 9.
The four structures analyzed with: (a) 5 directors; (b) 4 directors; (c) 3 close directors; (d) 3 spaced directors.
Figure 9.
The four structures analyzed with: (a) 5 directors; (b) 4 directors; (c) 3 close directors; (d) 3 spaced directors.
Figure 10.
Representation of the S parameters for the 4 different structures analyzed.
Figure 10.
Representation of the S parameters for the 4 different structures analyzed.
Figure 11.
Representation of the S parameters for different director lengths.
Figure 11.
Representation of the S parameters for different director lengths.
Figure 12.
Structures with different grounding dimensions: (a) 2 mm; (b) 4 mm; (c) 6 mm; (d) 10 mm; (e) total grounding.
Figure 12.
Structures with different grounding dimensions: (a) 2 mm; (b) 4 mm; (c) 6 mm; (d) 10 mm; (e) total grounding.
Figure 13.
S parameters for the structures with different grounding.
Figure 13.
S parameters for the structures with different grounding.
Figure 14.
The optimized structure: (a) modeled with HFSS; and (b) constructed on a Rogers RO3003 dielectric.
Figure 14.
The optimized structure: (a) modeled with HFSS; and (b) constructed on a Rogers RO3003 dielectric.
Figure 15.
S11 values obtained for the optimized structure: (a) measured; (b) obtained through numerical analysis.
Figure 15.
S11 values obtained for the optimized structure: (a) measured; (b) obtained through numerical analysis.
Figure 16.
Gain of the optimized structure.
Figure 16.
Gain of the optimized structure.
Figure 17.
Antenna with the 3 different tissues: (a) antenna placed on the skin; (b) antenna at a distance of 4 cm from the tissues.
Figure 17.
Antenna with the 3 different tissues: (a) antenna placed on the skin; (b) antenna at a distance of 4 cm from the tissues.
Figure 18.
SAR distribution on YZ transversal plane for: (a) initial antenna; (b) optimized antenna.
Figure 18.
SAR distribution on YZ transversal plane for: (a) initial antenna; (b) optimized antenna.
Figure 19.
SAR distribution in the tissue layers for the initial and optimized antenna: (a) skin; (b) adipose tissue; (c) muscle.
Figure 19.
SAR distribution in the tissue layers for the initial and optimized antenna: (a) skin; (b) adipose tissue; (c) muscle.
Figure 20.
SAR distribution on YZ transversal plane for a distance of 4 cm between antenna and tissues: (a) initial antenna; (b) optimized antenna.
Figure 20.
SAR distribution on YZ transversal plane for a distance of 4 cm between antenna and tissues: (a) initial antenna; (b) optimized antenna.
Figure 21.
Electric field distribution on YZ transversal plane: (a) initial antenna; (b) optimized antenna.
Figure 21.
Electric field distribution on YZ transversal plane: (a) initial antenna; (b) optimized antenna.
Figure 22.
Magnetic field distribution on YZ transversal plane: (a) initial antenna; (b) optimized antenna.
Figure 22.
Magnetic field distribution on YZ transversal plane: (a) initial antenna; (b) optimized antenna.
Figure 23.
Electric field distribution on YZ transversal plane for a distance of 4 cm between antenna and tissues: (a) initial antenna; (b) optimized antenna.
Figure 23.
Electric field distribution on YZ transversal plane for a distance of 4 cm between antenna and tissues: (a) initial antenna; (b) optimized antenna.
Figure 24.
Magnetic field distribution on YZ transversal plane for 4 cm between antenna and tissues: (a) initial antenna; (b) optimized antenna.
Figure 24.
Magnetic field distribution on YZ transversal plane for 4 cm between antenna and tissues: (a) initial antenna; (b) optimized antenna.
Table 2.
The directivity peak values for the studied structures.
Table 2.
The directivity peak values for the studied structures.
| Dielectric |
---|
Dimension | FR4 | RO3003 | RO4003C | RO4350B |
---|
0.51 mm | 4.0542 | 4.5328 | 4.46 | 4.37 |
1.51 mm | 3.6917 | 4.2514 | 4.2152 | 4.1446 |
Table 3.
The bandwidth for the studied structures.
Table 3.
The bandwidth for the studied structures.
| Dielectric |
---|
Dimension | FR4 | RO3003 | RO4003C | RO4350B |
---|
0.51 mm | 13.75% | 16.5% | 14.9% | 14.7% |
1.51 mm | 15.98% | 15.32% | 14.9% | 14.2% |
Table 4.
The bandwidth for the studied structures considering the increase in directors’ length.
Table 4.
The bandwidth for the studied structures considering the increase in directors’ length.
5 Directors | 5 Directors + 6 mm | 3 Directors | 3 Directors + 6 mm |
---|
16.51% | 23.31% | 16.22% | 22.64% |
Table 5.
The different peak gain values obtained for the grounding variation.
Table 5.
The different peak gain values obtained for the grounding variation.
2 mm | 4 mm | 6 mm | 8 mm | 10 mm | Total Grounding |
---|
4.3219 | 4.587 | 4.673 | 4.5551 | 4.4713 | 0.576 |
Table 6.
The bandwidths obtained for the grounding variation.
Table 6.
The bandwidths obtained for the grounding variation.
2 mm | 4 mm | 6 mm | 8 mm | 10 mm |
---|
18.32% | 18.99% | 19.66% | 23.31% | 17.96% |
Table 7.
Characteristic parameters for the considered tissue types.
Table 7.
Characteristic parameters for the considered tissue types.
Types of Tissue | | | |
---|
| Relative Permittivity | Conductivity | Loss Tangent |
---|
Skin | 38 | 1.46 | 0.283 |
Fat | 5.28 | 0.1 | 0.145 |
Muscle | 52.7 | 1.74 | 0.242 |
Table 8.
Radiated power density for the initial and optimized antennas.
Table 8.
Radiated power density for the initial and optimized antennas.
R (m) | for the Initial Antenna (W/m2)
| for the Optimized Antenna (W/m2)
|
---|
0.01 | 2937.754647 | 3851.540616 |
0.05 | 117.5101859 | 154.0616246 |
0.1 | 29.37754647 | 38.51540616 |
0.5 | 1.175101859 | 1.540616246 |
1 | 0.293775465 | 0.385154062 |
Table 9.
The maximal values accepted for the frequency of 2.4 GHz for the electric and magnetic field.
Table 9.
The maximal values accepted for the frequency of 2.4 GHz for the electric and magnetic field.
Exposure over 30 min | Exposure between 6 and 30 min |
---|
E | H | E | H |
---|
67.36 | 0.181 | 28.411 | 0.349 |