A 20 µW contact impedance sensor for wireless body-area-network transceiver

A low power contact impedance sensor (CIS) is presented for an energy efficient wireless body-area-network (WBAN) transceiver using a human body as a transmission medium. The proposed CIS adopts the capacitive sensing technique based on the LC resonance for detecting the parasitic capacitance between the electrodes and the human body to automatically turn on or off the transceiver. The 3´b resistive sensor, combined with a reconfigurable output driver in the transmitter, is proposed to compensate the channel quality degradation due to the contact impedance variation. It can reduce both the linearity and sensitivity requirements of the receiver front-end by 7 dB. It leads to significantly reduce the power of the LNA more than 70 % (from 2.0 mW to 0.6 mW). The proposed CIS of 1.0 mm × 1.4 mm is fabricated in 0.18 μm CMOS technology, and dissipates only 20 μW from 1.0 V.