Rat-Race Coupler Self-Interference Cancellation in Full-Duplex UE

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Solution Overview

Problem

Current methods for cancelling self-interference in full-duplex radio communication systems are inadequate, particularly due to limitations in passive cancellation using circulators, which fail to effectively address antenna mismatch-induced interference and result in significant signal losses and increased power consumption.

Innovation Solution

The use of a rat-race coupler in the user equipment (UE) to separate transmission and reception paths, combined with an RX diversity antenna, allows for efficient cancellation of self-interference signals by isolating and subtracting mismatch-induced signals, thereby improving cancellation performance and reducing power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If passive cancellation using circulators is used, then self-interference cancellation is attempted, but antenna mismatch-induced interference cannot be effectively addressed and signal losses increase

Engineering Contradiction:

Improveself-interference cancellation performanceVSAvoidsignal losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent introduces a circulator as an intermediary device between the transmit antenna and receive antenna. The circulator directs the transmitted signal away from the receive antenna while allowing the received signal to pass through to the receiver, thereby mediating the separation of transmission and reception paths and reducing self-interference

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent extracts the self-interference signal path from the received signal path by using a circulator to redirect the transmitted signal. This separation allows the receive antenna to capture only the desired downlink signal without the strong uplink transmitted signal, thereby removing the harmful interference component

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If passive cancellation using circulators is used, then self-interference cancellation is attempted, but power consumption increases

Engineering Contradiction:

Improveself-interference cancellation performanceVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by stationary object

Solution Approach 1:

The circulator serves as a passive intermediary device that uses magnetic fields generated by permanent magnets or ferrite materials to direct signal flow. This passive mechanism eliminates the need for active power-consuming components like amplifiers or processors to cancel self-interference

Inventive Principle:

Principle #24Intermediary (Mediator)

3Volume of moving object

If transmit and receive antennas are placed close together, then device compactness is improved, but self-interference increases due to strong transmitted signals being received

Engineering Contradiction:

Improvedevice compactnessVSAvoidself-interference

Core Design Contradiction:

Volume of moving objectVSObject-generated harmful factors

Solution Approach 1:

The circulator acts as a directional signal guide that allows the transmit antenna and receive antenna to be positioned close together while preventing the transmitted signal from reaching the receive antenna. The circulator's unidirectional signal flow property enables compact antenna placement without compromising self-interference rejection

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent segments the antenna system into distinct transmit and receive functional paths using the circulator. By separating the signal paths while maintaining physical proximity of antennas, the system achieves both compactness and effective self-interference cancellation

Inventive Principle:

Principle #1Segmentation

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 achieves superior self-interference cancellation performance, minimizing signal losses and power consumption, and enables integration of the RF front-end, with cancellation efficiency maintained across a wider frequency range compared to existing methods.

Implementation Method 1

a rat-race coupler, a plurality of transceiving (transmit/receive) antennas capable of transmitting and receiving signals; a receive antenna; a transmission (Tx) chain connected to an input port when the rat-race coupler uses one port as the input port, and a reception (Rx) chain connected to the receive antenna and an isolated port when the rat-race coupler uses the one port as the input port

Methodology Applied

Scientific EffectElectromagnetic isolation:

Data Source

PatentUS9571153B2Method of cancelling SI signal at RF-front end and UE for the same

Publication Date: 2017.02.14 LG ELECTRONICS INC

AI summary

A user equipment (UE) for cancelling a self-interference (SI) signal is disclosed. The UE includes a rat-race coupler, a plurality of transceiving antennas capable of transmitting and receiving signals, a receive antenna, a transmission (Tx) chain connected to an input port when the rat-race coupler uses one port as the input port, and a reception (Rx) chain connected to the receive antenna and an isolated port when the rat-race coupler uses the one port as the input port.