Abstract
The purpose of this research is to develop integrated analog-to-digital data converters (ADCs) which are suitable for the simultaneous acquisition of a large number (100 to 300) of electroencephalographic (EEG) signals. These signals are then processed by a computer. The EEG signals have narrow bandwidths, typically around 400 Hz, but their amplitudes are small and they need to be accurately acquired in the presence of high-level noise. This requires a large dynamic range, around 19 bits, for the devices implementing the data conversion. It is also preferable that the complete data acquisition structure be portable, and hence battery powered. This in turn requires low power dissipation by the data converters used.Sensor arrays detecting EEG signals have been successfully used in the noninvasive location of the sources of epilepsy in the brain [1],[2],[3]. Under this project we shall compare the available techniques (one ADC/channel, multiplexed delta-sigma ADCs, shared incremental ADCs) for this application. Using an ADC in each channel provides flexibility, but requires significant power dissipation, and may introduce mismatch effects. Conventional multiplexing of delta-sigma converters reduces power dissipation, but is subject to interchannel interference. Shared incremental data converters need more power than multiplexed delta-sigma ones, but they promise to be highly accurate under the specified conditions [4]. We shall compare these techniques by simulations, choose the most suitable method, and implement it by one or several integrated devices.To make sure that the devices developed under this research are truly useful for their intended applications, we shall interact with bioengineers active in the area of epilepsy diagnostics. Together, we shall establish a set of specifications for the multi-sensor array. Then, we shall develop the integrated ADC system which satisfies these specifications, and which is optimal for a portable sensor array.
[1] A.J. Fowle and C.D. Binnie, Uses and abuses of the EEG in epilepsy,” Epilepsia, 2000:41: S10-S18.
[2] G. Lantz et al., “Epileptic source location with high-density EEG: how many electrodes are needed?” Clinical Neurophysiology, 2003:114, pp.63-69.
[3] D.M. Tucker, “Spatial sampling of head electrical fields: the geodesic sensor net,” Electroencephalography and clinical neurophysiology, 1993:87, pp. 154-163.
[4] V. Quiquempoix et al., “A low-power 22-bit incremental ADC,” IEEE Journal of Solid-State Circuits, 2006:41, pp.1562-1571.
Report
Link to PDF: Final Report