Study the Effects of Misalignments in the Printed Spiral Inductive Coils for Passive Wearable Sensors

Misalignment-Tolerant Planar Spiral Coil Pair Design for 13.56 MHz Inductive Coupling of Wireless Resistive Analog Passive Sensors

“…As the secondary fill-factor has a negligible impact on the coupling factor; our focus is on minimizing the dependency of the coupling factor on the coil's relative position by optimizing the primary coil size and its fill-factor. We showed in [14] that the coupling factor and its uniformity (with coils' axial/lateral distance) increases with the primary coil size, as shown in Figure 5. In addition, the coil resistance increases by primary size, which leads to a lower sensitivity.…”

“…Therefore, we employ the Finite Element Analysis (FEA) simulation approach to determine the correlation between the coupling factor and the position of the coils. The accuracy of this approach has been validated in the previous report [14]. In summary, the dependency of sensitivity on coil position is derived by integrating the sensitivity-coupling factor analytical equation with the simulation curve for the coupling factor and coil position.…”

“…Therefore, the larger equivalent resistance in a larger primary coil decreases the sensitivity and, on the other hand, it slightly uniforms the coupling factor in lateral displacements. Considering the area occupied by the primary coil and according to Figure 5 (and results in [14]), 60 mm is taken as the optimal selection for the primary size, particularly for lateral distance less than 30 mm. Figure 6 shows the effect of the primary fill-factor (ϕ 1 ) on the coupling factor and its variation with lateral displacement for a primary size of 60 mm and an axial distance of 16 mm.…”

“…The coil optimization study on NFC and RFID techniques focuses on impedance matching and metal proximity [12,13]. We proposed our novel approach, utilizing a Genetic Algorithm, to design a pair of coils for maximum sensitivity ( [1,14]). The variable relative position of untied coils in a real setting degrades the optimized sensitivity through shifting the coupling factor of the coils.…”