Current-Domain OOK Receiver Circuit for Noise-Immune Isolation

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Solution Overview

Problem

On-off key (OOK) signal isolators face inefficiencies due to limited noise immunity and slow data rate transmission, primarily because of the use of multipliers and integrators in receivers, which struggle with common mode noise and high data rate applications.

Innovation Solution

A receiver system that processes OOK signals in the current domain, utilizing mismatched differential pair circuits and current mirrors to generate intermediate current signals, which are then converted to voltage representations by an output driver, enabling fast transitions between OOK states and improved noise immunity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a multiplier (or mixer) and an integrator are used as an energy detector for OOK demodulation, then the receiver can detect the presence or absence of the periodic signal, but the common mode noise handling ability is limited and the data rate transmission is slow

Engineering Contradiction:

Improvenoise immunityVSAvoiddata rate transmission speed

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The patent changes the operating domain from voltage to current by using current-mode circuits. The receiver generates an intermediate current signal that directly represents the OOK signal states, and uses current mirrors and differential pair circuits to process signals in the current domain, enabling fast transitions and improved noise immunity simultaneously

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the traditional voltage-mode multiplier and integrator system with a current-mode system using differential pair circuits and current mirrors. This substitution eliminates the need for slow integration operations while maintaining signal detection capability through direct current domain processing

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of operation

If a multiplier (or mixer) is used in the receiver, then the OOK signal can be demodulated, but the ability to handle common mode noise is limited

Engineering Contradiction:

Improvesignal demodulation capabilityVSAvoidcommon mode noise handling

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent employs mismatched differential pair circuits where the two transistors have intentionally different characteristics. This asymmetry allows the circuit to differentiate between the OOK signal states while being inherently more robust to common mode noise through the differential configuration that rejects equal disturbances on both inputs

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent introduces an intermediate current signal as a mediator between the input OOK signal and the final output. This intermediate current is generated through current mirrors and differential pairs, serving as a robust representation that maintains signal integrity while providing immunity to common mode noise before being converted to voltage by the output driver

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS10270630B2Demodulation of on-off-key modulated signals in signal isolator systems

Publication Date: 2019.04.23 ANALOG DEVICES INC

AI summary

A receiver system for an on-off key (“OOK”) isolator system may include a receiver that generates an intermediate current signal based on an OOK input signal. The intermediate current may be provided at a first current level when the input signal has a first OOK state and a second current level when the input signal has a second OOK state. The system also may include an output driver to generate a voltage representation of the intermediate current signal. Performing signal processing in a current domain permits fast transitions between OOK states.