Design of a mid-field wireless power transmission system for deep-tissue implants.

Background: Implantable medical devices are being valued as one of the developments of wireless biomedical technology.

Objective: This paper presents a mid-field wireless power transmission (WPT) system, which is designed for implantable applications and operates at the 2.40-2.48 GHz band of Industrial, Scientific, and Medical (ISM).

Methods: A new compact transmitter structure is proposed, and a small 4-C planar ring antenna is designed as the receiving element. A measurement setup is fulfilled on porcine tissues to verify the power transmission system.

Results: The experimental results show that the operating bandwidth is 2.2-2.62 GHz and the transmission coefficient can reach -26.32 dB at a distance of 50 mm. The effects of tissue differences, placement depth, and different transmission distances were also measured. The displacement and deflection tolerances between the transmitter and the implant receiver also have good performance. In the safety standard of specific absorption rate, for the 1 W output power from the mid-field transmitter, the receiving power of the implantable antenna at the mid-field distance can reach 79.6 mW.

Conclusion: With measurements of different implantation and transmission distance on pork, the mid-field power transmission efficiency is proven and shows the high performance of the system.