Printed spiral multi-coil based inductive-power-link for wireless sensor applications

Long-term operation of wireless sensors and obviation of the periodic battery replacement require either energy harvesting from the environment or wireless power transfer to the sensor units. Energy transfer using RF field proves to be an excellent way of transferring power to the sensor unit. This paper presents a detail design and optimization process of printed spiral coil (PSC) and PSC based efficient RF link to transfer power through magnetic field. The PSC has been designed and simulated using Agilent Design System (ADS) software. Simulated in ADS software, for a transmission distance of 2 cm with 1 KΩ load resistance and for a distance of 6 cm with 250 Ω load resistance the link efficiencies are found to be 79.09% and 58.46%, respectively. Based on the successful simulation results, a set of PSCs have been fabricated on FR4 substrate and the performances of the PSC and the PSC based inductive link are evaluated using HP4396B Network/Spectrum/Impedance Analyzer. Measurement results indicate an extended link distance for the multi-coil inductive link. Both simulation and measurement results show a great promise of PSC based multi-coil link for a wide variety of applications including but not limited to wireless powering of sensors, radio frequency sensing, magnetic resonance spectroscopy, etc.