Abstract
Emerging appli cations in brain–machine interface systems require high-resolution, chronic multisite cortical record- ings, which cannot be obtained with existing technologies due to high power consum ption, high invasiveness, or inability to transmit data wirelessly. In this paper, we describe a microsystem based on electrocorticography (ECoG) that overcomes these dif- ficulties, enabli ng chronic recording and wireless transmission of neural signals from the surface of the cerebral cortex. The device is comprised of a highly flexible, high-density, polymer-based 64-channel el ectrode array and a flexible antenna, bonded to 2.4 mm × 2.4 mm CMOS integrated circuit (IC) that performs 64-channel acquisition, wireless p ower and data transmission. The IC digitize s the signal from each electrode at 1 kS/s with 1.2 μV input referred noise, and transmits the serialized data using a 1 Mb/s backscattering modulator . A dual-mode power-receiving rectifier reduces data-dependent supply ripple, enabling the inte- gration of small decoupling capacitors on chip and eliminating the need for external components. Design techniques in the wireless and baseband circuits result in over 16× reduction in die area with a simultaneous 3× improvement in power ef ficiency over the state of the art. The IC consumes 225 μW and can be powered by an external reader transmitting 12 mW at 300 MHz, which is over 3× lower than IEEE and FCC regulations. Manuscript received April 28, 2014; revised August 03, 2014,