Energy Efficient Generic Demodulator for High Data Transmission Rate Over an Inductive Link for Implantable Devices

In this paper, we present a new Carrier Width Modulation (CWM) scheme for simultaneous transfer of power and data over a single inductive link. An ultra-low power CWM demodulator is also proposed. Unlike conventional demodulators for a similar modulation scheme, the proposed CWM circuit allows higher-speed demodulation and simple implementation. It works well as a generic demodulator operating at a frequency range between 10 and 31 MHz. It also supports a wide range of data rates under any selected frequency from the operating range. A CWM-based scheme encoding two-bit-per-symbol, called Quad-level CWM (QCWM) is also proposed. The latter allows high data-rates-to-frequency ratios. Using a 0.13-<inline-formula> <tex-math notation="LaTeX">$\mu m$ </tex-math></inline-formula> CMOS process and 1.2 V power supply, both CWM and QCWM demodulators were implemented and fabricated. They respectively occupy die sizes of 2137 and 3256 <inline-formula> <tex-math notation="LaTeX">$\mu m^{2}$ </tex-math></inline-formula> and dissipate, in worst conditions, 16.9 and 35.5 <inline-formula> <tex-math notation="LaTeX">$\mu W$ </tex-math></inline-formula>. Compared with state-of-the-art demodulators used for inductive forward data transmission, the proposed demodulators are distinctive given their low-energy efficiency and small silicon areas.