Development of Helical circular coils for wireless through-metal inductive power transfer

Reliable Through-Metal Wireless Communication Using Magnetic Induction

“…In these works, the frequency is selected by doing experiments and there is no guideline on the optimal frequency. More recently, [13] presents experimental results, which show that the optimal frequency for magnetic induction-based through-metal wireless power transfer is around 500 to 1000 Hz. Readers are referred to [6], [11] for a more complete review.…”

“…Thus, it is a promising solution for robots that are moving in metal-constrained environments. Although the optimal frequency based on experiments is reported in [13], there is a lack of analytical model to provide more insightful understanding, which is one of the motivations of this paper. The developed model can also advance our knowledge in many other domains, such as concrete wall monitoring [20].…”

“…is the angular frequency, µ i is the permeability, i is the complex permittivity, J 0 (x) is the zero order Bessel function of the first kind, ρ is the horizontal distance,R 12 is the reflection coefficient of the boundary between layer 1 and 2 considering the existence of layer 3, andT 13 is the transmission coefficient through the metal layer. H 3z is a key parameter to derive the mutual inductance between the transmitter and receiver, which determines the received power.…”

“…Similar as theT 13 , we can use the high-frequency approximations, i.e., k 1z = jk ρ and k 2z = k 2 , to derive the simplified R 12 , which is…”

“…As the carrier frequency reduces, the skin depth becomes large and the signal has better penetration efficiency [9]. This technology has been adopted in through-metal wireless power transfer and communications for more than one decade [9]- [13]. The achievable data rate and wireless power transfer efficiency are much lower than that of acoustic waves, but it does not rely on contact with metal surface, which is more flexible for mobile robots.…”