FDD Transceiver Interference Cancellation via Adaptive High-Pass Filtering

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Solution Overview

Problem

In Frequency Division Duplexing (FDD) communication systems, signal leakage from the transmitting chain to the receiving chain occurs due to insufficient isolation and non-ideal/nonlinearity effects of RF front-end components, causing interference to the received signal.

Innovation Solution

An interference cancellation method and module are introduced, which perform high-pass operations on both the to-be-sent and received signals, adjust filter coefficients adaptively, and generate a recover signal to eliminate interference. The module includes an energy module, first and second high-pass filters, and an adaptive filtering submodule to achieve this.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If transceiver hardware is miniaturized, then device size is reduced, but signal leakage from TX to RX increases

Engineering Contradiction:

Improvetransceiver sizeVSAvoidsignal leakage interference

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

An interference cancellation module is introduced as an intermediary component between the TX and RX chains. This module processes the received signal by subtracting the leaked TX signal component, effectively canceling the interference caused by signal leakage while allowing the transceiver to maintain its miniaturized form factor

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent applies asymmetric signal processing where the interference cancellation module processes signals differently based on their origin. The module identifies and cancels TX leakage components in the RX path while preserving the desired RX signal, creating an asymmetric treatment that resolves the interference problem without requiring symmetric hardware isolation

Inventive Principle:

Principle #4Asymmetry

2Object-affected harmful factors

If duplexer isolation is increased, then signal leakage is reduced, but device complexity and size increase

Engineering Contradiction:

Improvesignal leakage interferenceVSAvoidduplexer structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical/physical isolation approach (complex duplexer with multiple band-pass filters) with a signal processing approach. The interference cancellation module uses digital signal processing to cancel interference, substituting complex hardware isolation with simpler software-based interference cancellation algorithms

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If RF front-end components are improved for linearity, then interference is reduced, but manufacturing cost and complexity increase

Engineering Contradiction:

Improvenonlinearity interferenceVSAvoidmanufacturing cost

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent converts the harmful nonlinearity effects of RF front-end components into a manageable problem through signal processing. Instead of requiring expensive linear components, the interference cancellation module processes the nonlinear distorted signals and cancels the interference, effectively converting the manufacturing challenge into a software solution that reduces overall system cost

Inventive Principle:

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

Data Source

PatentUS10211931B1Method of interference cancellation and transceiving device

Publication Date: 2019.02.19 REALTEK SEMICON CORP

AI summary

A method of interference cancellation includes the following steps: performing a take-energy operation on a to-be-sent signal at multiple times to generate multiple to-be-sent signal powers; performing a first high-pass operation on the to-be-sent signal powers to generate a to-be-sent high-pass result; performing a second high-pass operation on a received signal to generate a received high-pass result; adjusting multiple filter coefficients according to the to-be-sent high-pass result and the received high-pass result; and generating a recover signal according to the filter coefficients.