Ultra-low-power RF transceivers for WBANs in medical applications

The paper presents two ultra-low-power ISM band RF transceivers for wireless body area networks (WBANs) in medical applications. Two RF transceivers with an asymmetric architecture are proposed to achieve high energy efficiency according to the asymmetric communication in WBANs. The 2.4 GHz transceiver consists of an OOK receiver (RX) with wake-up circuit (WuRx) and a BFSK/4FSK high speed transmitter (TX) with fast lock-in PLL. The 400 MHz transceiver consists of an OOK RX and a QPSK/8PSK/16QAM TX with a current-reused PLL. Different frequency bands and modulation schemes are adopted in the transceivers to fit different energy-efficient applications. Some novel circuit techniques: asymmetric transceiver architecture, phase-locked loop (PLL) synthesizer with a direct frequency presetting, passive wake-up circuit, and CMOS non-volatile memory (NVM) are used to reduce the power consumption and increase the performance. The transceivers are implemented in 0.18 um RF CMOS process. The max date rate of the TX is 7.5 Mbps with energy efficiency of less than 1 nJ/bit. The RX achieves a sensitivity of -55 dBm at a 100 kbps OOK data rate while consuming just 210 uW power.