Robust, reconfigurable, and power-efficient biosignal recording systems

Abstract

Wireless sensing of electrophysiological signals in day-to-day life will enable various clinical, research, and wellness applications. This paper reviews the design requirements of biosignal recording interfaces for use in remote, unconstrained environments and put the performance achieved by state-of-theart designs in perspective.In particular, we emphasize the need for biosignal recording front-ends to provide a dynamic range of approximately 100 dB, while meeting an input-referred noise level of a few µV rms. It is difficult to achieve a low input-referred noise and a high dynamic range using conventional voltage-domain amplifiers; state-of-theart designs provide only ∼60 dB of dynamic range. We propose to process electrophysiological signals in the phase domain, since there is no physical bound on phase. Low-noise VCO-based front-ends can be designed to extend the dynamic range by ∼40dB without paying a significant power, noise, or area penalty compared to state-of-the-art biosignal recording front-ends.For high-channel-count action-potential recording systems the system power is dominated by the transmitter if raw data is transmitted. In spite of the power reduction achieved by innovative biomedical transmitter designs, on-chip processing becomes necessary to reduce the output data rate for manychannel recording systems. It is important for neuroscientists and electrical engineers to agree upon a scheme to reduce the output data rate. We enlist and discuss a few data-rate reduction options for action-potential recordings. In addition, it is also desirable to make the biosignal sensors self-powered, thus avoiding the need for battery replacement/recharging. We briefly review existing energy-harvesting techniques and discuss future directions.

Next Generation Neural Interface Electronics

“…Particularly, when attempting to achieve a compact configuration with good linearity at these reduced supply voltages [112]. It should not be surprising that the use of oscillators have been particularly successful to leverage the digital design style [46]. Our group recently demonstrated that oscillator based structures, while high digital in nature, can allow exceptional performance for filtering time domain signals [59].…”

A 500 mVpp Input Range First-Order VCO-Based ADC with a Multi-Phase Quantizer for EEG Recording Front Ends

“…Additionally, suppressing kT/c noise in DT structures or maintaining the linearity of the G m -C filter in CT structures is often required [21]. To overcome the limitations of traditional voltage domain processing in advanced technology nodes, the EEG recording circuit topology based on a voltage-controlled oscillator (VCO) directly converts the input voltage to the frequency domain, thus avoiding the constraints imposed by the power supply voltage [22][23][24][25][26]. The frequency output of the VCO is quantized by measuring the phase increment over a specific time window.…”

High precision biomedical sensor readout circuits design for wearable health monitoring system

“…In [31], the idea of making use of VCO-based ADC frontend for bio-signal sensing is proposed. Instead of converting the input signal into voltage or current for quantization, the proposed model suggests a voltage-to-phase conversion.…”