A 1.1-mW Ground Effect-Resilient Body-Coupled Communication Transceiver With Pseudo OFDM for Head and Body Area Network

Abstract

This paper presents a body-coupled communication (BCC) transceiver (TRX) that mitigates all the practical impairments of the body channel at once. The proposed pseudo orthogonal frequency-division multiplexing (P-OFDM) TRX combines baseband BPSK-OFDM with frequency-shift keying (FSK) to alleviate the impacts of variable ground effect and variable skin-electrode contact impedance, which have been the two major issues on the BCC. It can tolerate up to 20 dB of channel gain variation with measured bit error rate improvement of > 70% compared to FSK modulation alone. The RC relaxed contact impedance monitor continuously monitors and compensates the variable skin-electrode contact impedance at both transmitter (TX) and receiver (RX). The proposed power-gated 8point inverse fast Fourier transform/fast Fourier transform with no floating-point multipliers (FPMs) reduces the gate count and power by 54% and 30% compared to conventional FPMs, respectively. Additionally, the simple floating-point adder (FPA) reduces the gate count and energy consumption by 34% and 20% compared to conventional FPAs, respectively. A high input impedance glitch-free FSK demodulation RX with variable threshold limiter and all digital cycle correction is also proposed to support a scalable data rate (200 Kbps-2 Mbps). The 0.54 mm(2) TRX in 65-nm CMOS consumes 1.1 mW.