Multiplexed Biopotential Recording Channels With Delta Encoding
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Solution Overview
Problem
Current biopotential signal processing technologies face challenges in achieving high electrode density, large spatial coverage, and efficient operation for both electrocorticography and single neuron recording, while also dealing with stimulation artifacts and power density limitations in bidirectional Brain-Computer Interfaces (BCBIs).
Innovation Solution
The development of a scalable, time-division multiplexed biopotential recording front-end using delta-encoded recording architecture with low-noise amplifiers and low-precision data converters, which implements delta encoding, multiplexing, and common-mode suppression to achieve high-precision recording with reduced silicon area and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If high electrode density and large spatial coverage are implemented, then recording capability is improved, but silicon area increases
Solution Approach 1:
The patent divides the recording system into multiple time-multiplexed channels that share common analog front-end components (amplifier, ADC, DAC). Each electrode channel is processed sequentially in time division, allowing many electrodes to be supported with a single shared analog processing chain, thereby reducing the silicon area required per channel while maintaining high electrode density capability
Solution Approach 2:
The patent implements a universal analog front-end that serves multiple electrode channels through time-division multiplexing. The same amplifier, ADC, and DAC are reused across multiple channels, making these components multi-functional. This universal approach enables support for large numbers of electrodes without proportionally increasing silicon area, as each component serves multiple purposes across different time slots
2Measurement precision
If high-precision recording is achieved, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent employs delta-sigma modulation which changes the representation parameters of the signal. Instead of directly quantizing the full-range biopotential signal with high-resolution ADCs, the system uses low-resolution ADCs (e.g., 1-bit or few-bit) that sample at higher rates, encoding precision information in the temporal pattern of pulses rather than in amplitude resolution. This parameter transformation allows high measurement precision to be achieved with low-power, low-resolution converters
Solution Approach 2:
The patent uses digital feedback to create a reconstructed version of the input signal and subtracts it from the original, creating a residual error signal that contains the high-precision information. This copying and subtraction process allows the system to achieve high effective bit precision through digital processing rather than through high-resolution analog-to-digital conversion, thereby reducing power consumption of the ADC while maintaining measurement precision
3Adaptability or versatility
If bidirectional operation (recording and stimulation) is implemented, then system versatility is improved, but stimulation artifacts interfere with recording
Solution Approach 1:
The patent implements time-division multiplexing where recording and stimulation operations are separated into different time slots. The system periodically switches between recording mode (where electrodes detect biopotential signals) and stimulation mode (where electrodes deliver electrical pulses). This periodic alternation ensures that stimulation artifacts do not contaminate recording signals, as they occur at different times, while maintaining bidirectional functionality within the same electrode array
Solution Approach 2:
The patent applies preliminary digital filtering and artifact suppression techniques to the recorded signals. Before full processing, the system identifies and removes stimulation artifact components from the recorded data using digital signal processing methods. This preliminary action cleans the recording signals of harmful stimulation artifacts, allowing bidirectional operation without cross-contamination between recording and stimulation functions
4Area of stationary object
If time-division multiplexing is used to reduce silicon area, then channel area is reduced, but processing complexity increases
Solution Approach 1:
The patent implements delta-sigma modulation with digital feedback loops in each time-multiplexed channel. The feedback mechanism compares the quantized output with the input signal, generates an error signal, and feeds it back to the next sampling interval. This feedback structure, while adding some processing complexity, enables the use of simple low-resolution ADCs and DACs, and the regular repetitive nature of the feedback operation allows for efficient digital implementation that does not excessively increase processing complexity despite the time-multiplexed architecture
Data Source
AI summary
Examples of recording channels and methods for biopotential signal acquisition and/or recording are described. Recording channels described herein may implement any combination of techniques described herein including multiplexing of multiple electrode inputs, delta encoding of biopotential signals, and common mode suppression.