PLL-Based Contactless Energy Transfer Analog FSK Demodulator Using High-Efficiency Rectifier

This paper proposes a new phase-locked-loop (PLL)-based inductive coupled contactless energy transfer (CET) analog frequency-shift keying (FSK) demodulator using a high-efficiency RF-to-dc rectifier for biomedical implanted devices. The analog FSK demodulator is composed of a modified CMOS three-stage rectifier, a voltage regulator, an FSK signal generator, and a PLL. The proposed modified single-stage rectifier with both positive and negative output voltages using a PMOS and an NMOS pass transistor, an inverter, and two capacitors has a small active area and can enhance the power conversion efficiency. The proposed RF-to-dc rectifier achieves an efficiency of 64% at 8.4 dBm. The power consumption of the demodulator is as low as 0.76 mW, and the active area is 0.084 mm². The analog FSK demodulator supports a data rate of 100 kb/s to 1 Mb/s. The chip was implemented in a Taiwan Semiconductor Manufacturing Company (TSMC) 0.35- μm double-poly quadruple-metal CMOS technology to verify the proposed CET circuit. Two figures of merit are provided to illustrate the advantages of the proposed architecture.