Bio-sensing SoC for wireless battery-less EEG-electrodes

Bio-sensing SoC

GAMMA2: Bio-sensing SoC for wireless battery-less EEG-electrodes

Technology: TSMC 0.18µm CMOS Log/MS/RF (G)

Prof. Harald Pretl, Stefan Schmickl

Overcoming extensive cabling

Trends show that electroencephalography (EEG) systems, used for either patient therapies or brain-computer-interfaces (BCI), tend to use more and more electrodes due to increased spatial resolution. With growing electrode count, the cabling process becomes a very time-consuming task. It is also practically impossible for the user to move because of the bulky cabling. 

Here the presented bio-sensing SoC GAMMA2 comes into play as replacement of a cabled solution.

Creating a SoC solution  

The SoC includes a power-management unit that consists of an RF-energy-harvester working in the 868 MHz UHF-band for wireless powering of the SoC, and a low-power LDO providing a constant voltage of 1 V to the subsequent units, giving a power budget of 5 µW for the total SoC. 

The digitized samples of the bio-signal get wirelessly transmitted with an ultra-wide-band (UWB) impulse-radio (IR) transmitter (TX). The UWB-IR-TX works at 7 GHz, sending with a data rate of 5.12 kbps and using a doublepulse-interval coded alphabet. It consumes only 1.89 µW. 

Enabling a high amount of wireless sensing channels  

The used transmission scheme allows up to 64 sensor nodes to work at the same time, enabling a high amount of wireless sensing channels. Indoor wireless transmission experiments showed a range of over 12 m, together with a custom made UWB-receiver.

GAMMA2 prototype, shown in the center, as replacement of a cabled solution. 

Measured EEG-signal, showing blinking eyes.

Micrograph of GAMMA2 SoC.