Cross Interference Free Dual Frequency Wireless Power Transfer Using Frequency Bifurcation for Dynamic Biomedical Implants

Multiple biomedical implants are used in different applications to monitor the functions of living cells. The inductive resonant coupled wireless power transfer (WPT) has been investigated extensively to increase the lifetime and reduce the battery size of implants. The concurrent WPT to multiple devices is one of the unique features of inductive resonant coupling. However, the cross-coupling among the multiple implants during the concurrent power transfer raises the issue of interference between the implants. It affects both the power and data transfer rate, which leads to malfunction of implantable sensor. This article proposes a simple and effective approach of eliminating cross interference using resonant frequency bifurcation technique. Two overcoupled resonant coil structures are investigated at the transmitter (Tx) side to concurrently power two implants that are non-stationary. In addition, a dual frequency impedance matching circuit is developed to maintain the required bifurcated frequency at the Tx section regardless of changes in coupling between implanted coil and Tx side coil. The simulation and experimental outcomes predict that the proposed technique is able to provide 29.35% of power transfer efficiency at the chosen source frequency of 6.78 MHz.