Always-On IMD Receiver with Antiphase Offset Correction

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Solution Overview

Problem

Implantable medical devices face challenges in conducting reliable low-amplitude implant-to-implant communication due to traditional differential amplifiers' high input offset voltage and susceptibility to drift, which can lead to synchronization issues in dual chamber pacemaker systems.

Innovation Solution

The implementation of a redundant parallel fully differential auto-zeroed system using two differential amplifiers that are selectively enabled and offset corrected in antiphase, allowing for continuous monitoring of low-frequency wakeup signals while minimizing power consumption, and enabling a high-frequency receiver only when necessary.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a traditional differential amplifier is used to receive low-amplitude implant-to-implant signals, then the receiver can detect signals, but the input offset voltage (typically 10 mV or more) will be greater than the signal amplitude (under 1 mV), making detection unreliable

Engineering Contradiction:

Improvesignal detection capabilityVSAvoiddetection reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent changes the electrical parameters of the differential amplifier by implementing auto-zeroing circuitry that periodically measures and compensates for input offset voltage, thereby transforming the amplifier's characteristics to enable reliable detection of low-amplitude signals below 1 mV

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If a traditional differential amplifier is used for continuous monitoring, then signals can be detected, but the amplifier is susceptible to input offset voltage drift over time and temperature, degrading performance

Engineering Contradiction:

Improvesignal detection accuracyVSAvoidoffset voltage stability

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The patent implements a feedback mechanism where the differential amplifier periodically measures its own input offset voltage through auto-zeroing circuitry and applies compensating signals to cancel the offset, thereby maintaining stable and accurate signal detection despite temperature variations and time drift

Inventive Principle:

Principle #23Feedback

3Measurement precision

If both differential amplifiers are continuously enabled for offset correction, then offset voltage is minimized, but power consumption increases significantly

Engineering Contradiction:

Improveoffset correction accuracyVSAvoidbattery power consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent implements periodic offset correction where each differential amplifier alternates between active signal monitoring and offset correction phases, performing auto-zeroing at predetermined intervals rather than continuously, thereby maintaining measurement precision while significantly reducing average power consumption from the battery

Inventive Principle:

Principle #19Periodic action

4Measurement precision

If one differential amplifier is placed in offset correction phase, then offset voltage is reduced, but the amplifier becomes blind to incoming signals during correction

Engineering Contradiction:

Improveoffset voltage accuracyVSAvoidsignal detection during correction

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

The patent divides the receiver function into two parallel differential amplifiers that operate in complementary phases, allowing the system to segment the time-domain operation such that while one amplifier corrects offset, the other remains active for signal detection, eliminating blind periods

Inventive Principle:

Principle #1Segmentation

5Adaptability or versatility

If the high-frequency receiver is always enabled, then all communication signals can be received, but power consumption increases

Engineering Contradiction:

Improvecommunication capabilityVSAvoidbattery power consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The patent implements dynamic receiver management where the high-frequency receiver is selectively enabled only when low-frequency wakeup signals are detected, allowing the system to adapt its communication capabilities in real-time based on incoming signal requirements, thereby reducing power consumption while maintaining versatility

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS11207534B2Always on receiver with offset correction for implant to implant communication in an implantable medical system

Publication Date: 2021.12.28 PACESETTER INC

AI summary

Disclosed herein are implantable medical devices (IMDs) including a receiver and a battery, and methods for use therewith. The receiver includes first and second differential amplifiers, each of which monitors for a predetermined signal within a frequency range and drains power from the battery while enabled, and while not enabled drains substantially no power from the battery. To remove undesirable input offset voltages, each of the differential amplifiers, while enabled, is selectively put into an offset correction phase during which time the predetermined signal is not detectable by the differential amplifier. At any given time at least one of the first and second differential amplifiers is enabled without being in the offset correction phase so that at least one of the differential amplifiers is always monitoring for the predetermined signal. In this manner, the receiver is never blind to signals, including the predetermined signals, sent by another IMD.