Paper Title
Excellent Wireless Power Transfer Unto Tiny Coil Using 4-Coil Strongly Coupled Magnetic Resonance (SCMR) For Implantable Devices And Biosensors

Abstract
In this paper, a novel 4-Coil strongly-coupled-magnetic-resonance (SCMR) system for wirelessly powering miniaturized biosensors and implanted devices is proposed and analyzed. The receiver (Rx) coil is a tiny hair-pin inductor of 110 m on a lossy silicon substrate, and the relatively large transmit (TX) coil is of a diameter of 1.4 mm designed on a FR4 substrate. The 4-coil SCMR system has a TX coil, a RX coil and two relay coils between them, where the closest distance from the relay coil to the RX coil is fixed at 1 mm. The 4-coil SCMR system is then compared with a corresponding 2-coil resonant inductive coupling system, where the RX-to-TX coil spacing is also kept at 1 mm. The RX coil for each system is identical, consisting of a tiny on-chip inductor used for energy harvesting to power up miniature devices. This 2-coil system is compared with the 4-coil system on the wireless power coupling efficiency, where the Tx and RX coils for each system are connected to their respective resonant tuning capacitors to resonate at 5.8 GHz. 3-Dimensional electromagnetic (EM) simulations show the optimized 4-coil system consistently outperforms the optimized 2-coil system in wireless power transfer (WPT) by 5-6 dB, reaching an impressive a wireless power coupling of ~ -26.5 dB unto the tiny RX coil. Keywordsó Inductive Power Coupling, Resonant inductive coupling, Strongly Coupled Magnetic Resonance (SCMR), Wireless Power Transfer (WPT).