'Institute of Electrical and Electronics Engineers (IEEE)'
Doi
Abstract
This paper describes a low-power/low-voltage CMOS
wireless interface (CMOS-WiI) at 5.7 GHz with dry electrodes for
congnitive networks. The electrodes are 4 x 4 microtip arrays and
acquire electroencephalogram (EEG) signals in key- points for
processing. The CMOS-WiI was fabricated in a UMC 0.18 µm
RF CMOS process and its total power consumption is 23mW with
a voltage-supply of only 1.5 V. The carrier frequency is digitally
selectable and it can be one of 16 possible values in the range
5.42–5.83 GHz, with 27.12 MHz steps. These multiple carriers
allow a better spectrum allocation as well as the acquisition,
processing and transmission of high-quality EEG signals from 16
electrode arrays. The microtips array was fabricated through bulk
micromachining of a -type silicon substrate in a potassium
hydroxide solution and avoids long subject preparations for EEG
data acquisition. The reactive sputtering of iridium dioxide (IrO)
on the surface of the array guarantees its biocompatibility. The
fabrication process was trimmed in a way that each microtip
presents solid angles of 54.7 , a width in the range 150–200 µm, a
height of 100–200 µm, and a microtip interspacing of 2 µm. The
microtips array coated with IrO together with the CMOS-WiI
permit the remote monitoring of EEG signals from freely-moving
subjects