Efficiency Enhancement of Wireless Powering Process for Low Impedance Biosensors

Wireless charging of biosensors represents a significant advancement in biomedical devices, especially in wearable and implanted health monitoring systems. This approach uses magnetic resonator coupling to transmit energy without physical connections, hence enhancing patient comfort and mobility, unlike conventional batteries. This paper discusses a transmitting coil powered by a class-E RF power amplifier operating at a frequency of 5 MHz, which energizes two parallel receiving coils positioned 2 × 10−3 meters apart and located 2 × 10−2 meters away from the transmitter. This arrangement establishes a loosely coupled inductive link. The proposed wireless power transfer (WPT) system is designed for low impedance biosensors affixed to the human skin surface or implanted beneath the skin for biosignal detection, hence eliminating the need for resonant capacitors on the receiving end. The simulation results demonstrate that the use of parallel coils on the receiving side of a wireless power transfer system markedly enhances link efficiency compared to a single receiving coil. The proposed system achieved a maximum link efficiency of 14.5% at a load resistance of 7.5Ω, exceeding the efficiency of 11.25% achieved by the single receiving coil configuration under identical load conditions. The proposed system is appropriate for low impedance loads, particularly biosensors. This is corroborated by the simulation results. The greatest DC power extracted from the DC source is 2.85W, which is markedly low in relation to the operational efficacy of such systems. It is feasible to improve output power and inductive link efficiency by reducing the distance between transmitting and receiving coils.