Wireless Biopotential Acquisition Systems

The low-noise and low-power analog readout front-end ASICs of this book may open the doors towards the miniaturization of low-cost and high-performance wireless biopotential acquisition systems that can improve the patients’ autonomy and quality of life. This Chapter presents the wireless biopotential acquisition systems that make use of the analog readout front-end circuits presented in Chap. 4. All of the wireless biopotential acquisition systems include a state-of-the-art low-power microcontroller, a state-of-the-art low-power radio, and a custom designed antenna.

The low-power microcontroller is the MSP430 from Texas Instruments [Texas-Instruments, “MSP430F149 mixed signal microcontroller datasheet”, online, June 2004]. It consumes 0.6 nJ/instruction active power. Its low stand-by power (2 μW) and fast wake-up time enables the duty-cycled operation of the microcontroller. Furthermore, the built-in ADC can be used to digitize the analog output of the biopotential readout front-end ASICs.

The low-power radio is the nRF2401 2.4 GHz transceiver from Nordic [Nordic-VLSI, “nRF2401A ultra low-power 2.4GHz transceiver”, http://nvlsi.no]. It is capable of transmitting at a maximum data rate of 1 Mbit/s. Thus, the low data-rate applications can be operated in burst mode, transmitting the data at high data-rates and turning off the transceiver during the rest of the time, in order to decreases the power dissipation. The supply current of the transceiver is 8 mA, when transmitting at −5 dBm, and 15 mA in receive mode. The antenna of each system is a custom designed integrated dipole antenna, which takes into account the close proximity of the human body [S. Brebels et al. in Electronic Components and Technology Conference, 2005. Proceedings. 55th, vol. 231, pp. 1602–1606, May–3 June 2005].