A Differential Analog Receiver Front-End for Galvanic-Coupled Human Body Communication

The galvanic-coupled human body communication (HBC) has come out as an alternative to radio frequency communication for connecting miniaturized wearable, implantable devices in, on the human body. The existed researches focused on the channel characteristics measurement, less on transceiver. The analog front-end (AFE) circuit is the significant part of the transceiver. In this paper, a wearable AFE circuit for human body communication is proposed, which can be utilized for subsequent signal recovery or demodulation. Differential input and filter hold circuits are used to get rid of interference from the environment and the human body. The variable gain amplifier module is applied as the final stage amplifier to reduce the influence of the change caused by the contact instability of the output electrodes. The performance index of the front-end circuit is obtained by analyzing the experimental results. The results show that the circuit has a high gain flatness. When the circuit gain is 40 dB, the gain error is within ± 0.5 dB in the frequency range of 10kHz-1MHz. The common-mode rejection ratio of the circuit can reach 112 dB, and the voltage equivalent input noise is only 3 nV/√Hz, which can guarantee the stability of HBC in complex situations. In the end, the effectiveness of the analog front-end circuit is verified by in vivo experiments.