A multi-cycle Q-modulation technique for wirelessly-powered biomedical implants

This paper presents a new technique, called multicycle Q-modulation, which can be used in wireless power transmission (WPT) to modulate the quality factor (Q) of the receiver (Rx) and dynamically match the load impedance with that of the inductive link. A key advantage of the proposed Q-modulation method is that it can be easily implemented using off-the-shelf power management components without requiring any fast switching function at the carrier frequency, which is only feasible in integrated circuit implementation. The multi-cycle Q-modulation is analyzed theoretically by a lumped circuit model, and verified in simulation and measurement using an off-the-shelf receiver. In a conventional 2-coil link, the proposed method increases the power amplifier (PA) plus inductive link efficiency from 1.2% to 12.8% at RL = 1 kΩ, and from 17.8% to 24.5% at RL = 50 Ω with 170 mW power delivered to the load.