Antenna-Based Self-Interference Cancellation Circuit

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Full-duplex wireless systems face significant challenges due to strong self-interference, which exceeds the receiver noise floor, making it difficult to achieve effective wireless capacity enhancement.

Innovation Solution

The implementation of antenna-based self-interference cancellation circuits using a transmit antenna, a cross-polarized receive antenna, and an auxiliary port with a reflective termination that counters interference by reflecting a signal to cancel out the impact of the transmit signal at the receive port, achieving more than 50 dB of cancellation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If full-duplex operation is implemented to improve wireless capacity, then wireless capacity is improved, but self-interference becomes stronger than the receiver noise floor

Engineering Contradiction:

Improvewireless capacityVSAvoidself-interference

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent divides the receive antenna into two separate ports: a receive port cross-polarized with the transmit antenna for receiving weak signals, and an auxiliary port co-polarized with the transmit antenna for capturing self-interference. This segmentation allows the system to separately process and cancel self-interference while maintaining weak signal reception capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent converts the harmful self-interference signal into a useful cancellation signal by capturing it through the auxiliary port, processing it through a reflection coefficient, and subtracting it from the receive port signal. The harmful interference is transformed into a benefit by enabling full-duplex operation.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Object-affected harmful factors

If antenna-based self-interference cancellation is implemented to suppress self-interference, then self-interference is suppressed, but device complexity increases

Engineering Contradiction:

Improveself-interferenceVSAvoiddevice complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent introduces an auxiliary port as an intermediary element that captures self-interference without affecting the main receive path. This intermediary structure provides a clean separation between interference capture and signal reception, simplifying the overall cancellation architecture compared to processing the entire receive signal.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent utilizes polarization as a key parameter to differentiate between the transmit antenna, receive port, and auxiliary port. By designing the auxiliary port with co-polarization matching the transmit antenna and the receive port with cross-polarization, the system achieves automatic interference separation based on polarization parameters, reducing the need for complex active cancellation components.

Inventive Principle:

Principle #35Parameter changes

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 solution effectively suppresses self-interference, maintaining cancellation across various environments by reconfiguring the termination, thereby enhancing wireless capacity and improving system performance.

Implementation Method 1

a termination connected to the auxiliary port that reflects a signal received at the auxiliary port as a reflected signal

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

a receive antenna having a receive port that is cross-polarized with respect to the transmit port and having an auxiliary port that is co-polarized with respect to the transmit port

Methodology Applied

Scientific EffectPolarization: Polarisation

Data Source

PatentUS10090585B2Circuits and methods for antenna-based self-interference cancellation

Publication Date: 2018.10.02 THE TRUSTEES OF COLUMBIA UNIV IN THE CITY OF NEW YORK

AI summary

Circuits and methods for antenna-based self-interference cancellation are provided. In some embodiments, circuits for antenna-based self-interference cancellation are provided, the circuits comprising: a transmit antenna having a transmit port that receives a transmit signal; a receive antenna having a receive port that is cross-polarized with respect to the transmit port and having an auxiliary port that is co-polarized with respect to the transmit port; and a termination connected to the auxiliary port that reflects a signal received at the auxiliary port as a reflected signal, wherein the reflected signal counters interference caused by the transmit signal at the receive port.