Biphasic Pulse Signal Coding With Refractory Rate Limiting
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Solution Overview
Problem
Conventional devices face challenges in reducing power consumption and data bandwidth while processing analog signals digitally, particularly in power-restricted applications like biomedical implants, due to the inefficiencies of Nyquist-Rate and Delta-Sigma converters, and the peak spiking rates in integrate-and-fire signal representation methods.
Innovation Solution
A unique asynchronous biphasic pulse signal coding technique that transforms continuous-amplitude, continuous-time signals into discrete-time signals, reducing front-end complexity and allowing for simpler, lower power circuitry, and introduces a refractory period to bound peak firing rates, thereby reducing data bandwidth and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Nyquist-Rate A/D converters are used to convert analog signals to digital form, then signal processing can be performed digitally with robust transmission and storage, but power consumption increases significantly
Solution Approach 1:
The patent replaces the conventional A/D converter (analog-to-digital conversion system) with an integrate-and-fire neuron system that directly encodes analog signals into digital-like spike trains through biological-inspired mechanisms, avoiding the power-consuming Nyquist-Rate sampling architecture while maintaining signal robustness
Solution Approach 2:
The patent changes the fundamental parameter of signal representation from continuous amplitude values (analog) to discrete spike timing patterns (event-based digital), using the integrate-and-fire mechanism to transform signal parameters and enable low-power processing
2Device complexity
If Delta-Sigma converters are used to relax analog circuitry requirements, then analog circuit complexity decreases, but digital circuit complexity and power consumption increase due to high-speed clock requirements
Solution Approach 1:
The patent uses periodic refractory periods in the integrate-and-fire neuron system to naturally limit the firing rate, replacing the need for high-speed clocks in Delta-Sigma converters while achieving similar signal encoding functionality with lower power consumption
Solution Approach 2:
The patent substitutes the high-speed digital clocking mechanism of Delta-Sigma converters with a biological-inspired integrate-and-fire mechanism that uses membrane potential integration and threshold-based spiking, eliminating the need for high-frequency periodic sampling
3Ease of operation
If DC bias is added to make the analog signal strictly positive for IF neuron encoding, then the signal can be processed by IF neurons, but power is wasted due to the worst-case offset shift
Solution Approach 1:
The patent segments the signal processing into two independent IF neurons: one handling positive signal excursions and another handling negative signal excursions. This segmentation eliminates the need for DC bias by allowing each neuron to respond only to its designated polarity, thereby avoiding the power waste associated with worst-case offset shifts
4Measurement precision
If the peak firing rate is unbounded in IF signal representation, then information can be encoded with high temporal resolution, but data bandwidth increases and power consumption increases
Solution Approach 1:
The patent introduces periodic refractory periods that temporarily disable the IF neuron after each spike, creating a natural upper bound on the firing rate. This periodic inhibition maintains temporal resolution for information encoding while limiting the peak data bandwidth to the inverse of the refractory period duration
Data Source
AI summary
A method for coding time signals based on generating an asynchronous biphasic pulse train is provided. The method includes generating response signals based upon one or more input signals. A pulse comprises a positive pulse if a voltage of the response signal is greater than a predetermined positive voltage threshold. A pulse comprises a negative pulse if the voltage of the response signal is less than a predetermined negative voltage threshold. The method further includes a method for the reconstruction of a uniformly sampled version of the original signal.