Wireless transceiver for EEG monitoring meets medical and BAN specs; under 2 mW Tx

February 12, 2014 // By Graham Prophet
A co-operation between Fujitsu Laboratories and imec’s Holst Centre has yielded a transceiver design that complies with the 400 MHz-band international standard while consuming 1/10th the power of previous models, lightening the burden on monitored patients who need carry lighter instruments with smaller batteries.

The Kawasaki, Japan, labs of Fujitsu, and imec Holst Centre in Eindhoven (Netherlands) jointly designed the wireless transceiver circuit for use in body area networks (BAN) for medical applications.

Wireless monitoring of brainwaves or other vital signs has in the past required over a dozen milliwatts (mW) of electric power, a limitation on the ambulatory monitoring that medical researchers and clinicians would like to deploy. By optimising architecture and circuitry, Fujitsu Labs and Holst Centre designers have reduced the power requirements of a wireless transceiver front-end to 1.6 mW when receiving data and 1.8 mW when transmitting.

This technology extends by approximately ten-fold the battery life of conventional sensor products used for patient monitoring. This cuts the frequency of battery replacement or recharges, lightens the burden on patients, and increases the work efficiency of medical practitioners.

Based on this joint research into wireless transceiver technology, Fujitsu Laboratories plans to apply it to non-medical uses, such as to the monitoring of societal infrastructure.

This research project stipulated a 400-MHz wireless specification compliant with IEEE 802.15.6, the international standard for BANs, and support for two independent modes: a 4.5 Mbps high-speed mode capable of transmitting brainwaves, images, and other data needed in medicine, and an 11.7 kbps low-speed, low-power mode for low-power operations when sensor nodes are on standby.

The diagram illustrates two key aspects of the design;

Digitally controlled receiver technology;

Simplifying the architecture of the transceiver circuit as much as possible has resulted in lower power demands. The digitally controlled transceiver circuit uses a programmable structure that can change its circuitry characteristics to support different phase and frequency modulation methods in adherence to BAN international standards. The receiver consists of a low-noise amplifier, mixer, low-pass filter, and A/D converter, and uses direct-conversion (zero-IF) approach. The use of this technique, along with minimised power requirements for all of the constituent circuitry, made it possible to greatly reduce power requirements. The 4.5-Mbps