Exploiting Electrocorticographic Spectral Characteristics for Optimized Signal Chain Design: A 1.08 W Analog Front End With Reduced ADC Resolution Requirements<formula formulatype="inline"> <tex Notation="TeX"/> </formula>

Abstract

Electrocorticography (ECoG) is an important area of research for Brain-Computer Interface (BCI) development. ECoG, along with some other biopotentials, has spectral characteristics that can be exploited for more optimal front-end performance than is achievable with conventional techniques. This paper optimizes noise performance of such a system and discusses an equalization technique that reduces the analog-to-digital converter (ADC) dynamic range requirements and eliminates the need for a variable gain amplifier (VGA). We demonstrate a fabricated prototype in 1p9m 65 nm CMOS that takes advantage of the presented findings to achieve high-fidelity, full-spectrum ECoG recording. It requires 1.08 μW over a 150 Hz bandwidth for the entire analog front end and only 7 bits of ADC resolution.

Phase Synchronization Operator for On-Chip Brain Functional Connectivity Computation

“…This makes low frequency bands more tolerant to the aggregated noise contributed by biological tissue, electrodes and recording front-ends [39], [40]. Indeed, it has been shown that even with modest amplifier noise specifications, without suppressing flicker contributions, SNRs larger than 30 dB can be obtained at low frequencies [41]. This suggests that PS calculations can be relevant as a neurological biomarker in the β and lower frequency bands although the reliability decreases for the high-γ band and higher frequencies.…”

A Sub-μVRms Chopper Front-End for ECoG Recording

“…Some of them obtain very low noise and low power performance [10], however they do not include methods to deal with the large DC offsets at the electrode-tissue interface. In other cases, the front-end exhibits low input impedance [4], high power consumption [8] or high input-referred noise [9].…”

A 14-ENOB Delta-Sigma-Based Readout Architecture for ECoG Recording Systems

“…An additional challenge is the high dynamic range associated with bio-potential measurements [4], [9], [12]- [14]. For instance, an electrocortical (ECoG) signal is usually sensed, as depicted in Fig.…”

“…The most straightforward method of rejecting the electrode offset is by AC coupling, which performs passive high-pass filtering with a very low cut-off frequency [14], [21]- [23]. However, the total common-mode rejection is limited by the capacitor matching accuracy, which is further deteriorated by the impedance unbalance between the sensing and reference terminals of the analog front-end [24], [25].…”