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

Abstract

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-μm 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 μm2 and dissipate, in worst conditions, 16.9 and 35.5 μW. 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.

Keywords

• Carrier width modulation
• demodulator
• downlink data transmission
• inductive link