| Popis: |
Inductive coupling between two coils is becoming an important technique for wireless power and data transfer in near-field for a variety of applications such as wireless charging and passive (zero-power) sensors. We have previously employed a pair of printed spiral coils (PSC) to collect the physiological signals via our novel Wireless Resistive Analog Passive (WRAP) skin attachable sensors. The pair of PSCs and the circuit components have been optimized to maximize the probed biosignals where the mutual inductance (or coupling factor) was kept constant. However, the coils' relative positions in the wearables can vary in real-life scenarios, which makes the mutual inductance to change, compromising optimal results. To design a system with maximum robustness against these PSC alignment variations, the effects of primary coil size on the coupling factor variability to axial and lateral displacements are studied. We limited the maximum self-inductance to 5 µH and 7 µH for primary and secondary coils, respectively that ensures the results are not affected by the coils' self-inductance variation. Our simulation shows that larger primary coils create magnetic fields with reduced sensitivity to the coupling factor for lateral and axial displacements. The resultant coupling factor behavior indicates robust coil designs for applications where the axial and lateral displacements can occur in real-life. |
