Full-Duplex Communication Circuit With Differential Signal Subtraction

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Solution Overview

Problem

Existing full duplex communications circuits face challenges with signal subtraction errors and complexity, particularly in noise reduction and synchronization, often requiring multiple current sources and circuit components, which increase costs and implementation difficulties.

Innovation Solution

A full duplex communications circuit design utilizing first and second current sources, resistive circuits, interface circuits, and transistor-based driver circuits, along with differential amplifiers, generates a differential output signal by subtracting a power-related value across a resistive circuit from a reference value, facilitating signal extraction and noise reduction through cascode filters and diodes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If signal subtraction is used to receive correct transmitted signal, then full duplex communication is enabled, but signal subtraction errors and noise increase

Engineering Contradiction:

Improvefull duplex communication capabilityVSAvoidsignal subtraction accuracy

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent transforms the subtraction operation from the time domain to the frequency domain using Fourier transforms. By changing the domain parameter from time-based signal subtraction to frequency-based spectral subtraction, the system achieves more accurate noise cancellation and reduced subtraction errors, resolving the contradiction between enabling full duplex communication and maintaining signal accuracy.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If synchronization is implemented for noise reduction, then signal quality improves, but implementation difficulty increases

Engineering Contradiction:

Improvesignal qualityVSAvoidsynchronization implementation complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical/time-domain synchronization approach with a frequency-domain correlation method. Instead of requiring precise temporal alignment through complex synchronization circuits, the system uses cross-correlation in the frequency domain to automatically identify and align signal components, significantly reducing implementation complexity while maintaining signal quality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If multiple current sources and circuit components are used, then communication performance improves, but cost and complexity increase

Engineering Contradiction:

Improvecommunication performanceVSAvoidcircuit component quantity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines multiple signal processing functions (transmission, reception, noise cancellation, and signal extraction) into a unified frequency-domain processing framework. By merging these previously separate functions into a single integrated approach using Fourier transforms and spectral subtraction, the system achieves improved communication performance while reducing the number of discrete circuit components required.

Inventive Principle:

Principle #5Merging (Combining)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach enables accurate signal extraction and noise reduction, simplifying the implementation of full duplex communications while reducing complexity and cost by using a common set of amplifier circuits and differential amplifiers to detect signals on a communications medium.

Implementation Method 1

a differential output circuit generates an output signal corresponding to a signal received via the communications medium at the interface circuit, based upon a power-related value across the first resistive circuit, less a power-related value across the second resistive circuit

Methodology Applied

Scientific EffectSignal subtraction:

Implementation Method 2

The first transistor-based driver circuit is coupled between the first current source and each of the first and second resistive circuits, and the second transistor-based driver circuit is coupled between the second current source and each of the first and second resistive circuits

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS8817670B2Full duplex communication circuit and method therefor

Publication Date: 2014.08.26 NXP BV

AI summary

Duplex communications are facilitated. In connection with various example embodiments, current sources are used to drive transistor-based circuits coupled across a first resistive circuit, to send signals on a communications medium. While driving the transistor-based circuits, the current sources are used to drive reference transistor-based circuits coupled across a second resistive circuit. A differential output signal based upon a power-related value across the first resistive circuit, less a power-related value across the second resistive circuit. This differential output signal characterizes a power-related value corresponding to a received signal on the communications medium, as gleaned from a total signal corresponding to both transmitted and received signals, less a signal corresponding to the transmitted signal.