Digital Transmitter Interference Cancellation in RF Transceivers

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Solution Overview

Problem

Existing transceiver systems face challenges in effectively canceling transmitter interference due to insufficient duplexer isolation, requiring complex amplitude phase adjustments that are not adequately addressed by current methods which only perform complex number multiplication on analog signals.

Innovation Solution

The method involves coupling a part of radio frequency signals from the transmitter, processing them into digital signals using an interference receiver, and performing interference cancellation in the digital domain, employing techniques like FIR, IIR filtration, FFT, and frequency domain amplitude phase weighting to achieve more complex amplitude phase adjustments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If analog amplitude phase adjustment is used, then the structure is simple, but the adjustment capability is insufficient when in-band amplitude phase property is not flat

Engineering Contradiction:

Improvestructure simplicityVSAvoidamplitude phase adjustment capability

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The patent replaces the analog amplitude phase adjustment mechanism (mechanical/electrical system) with a digital signal processing system. Specifically, it uses digital complex number multiplication and adaptive filtering algorithms to perform amplitude and phase adjustments on the interference signal, enabling precise compensation of non-flat in-band amplitude and phase characteristics that cannot be achieved with simple analog components.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating domain from analog to digital, allowing dynamic adjustment of amplitude and phase parameters through software-controlled digital signal processing. The system can adaptively modify filtering coefficients and complex multiplication factors to compensate for varying in-band amplitude and phase properties, providing flexibility that fixed analog circuits cannot achieve.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If duplexer isolation is increased, then transmitter interference is reduced, but production cost increases

Engineering Contradiction:

Improvetransmitter interferenceVSAvoidproduction cost

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent converts the harmful transmitter interference signal into a useful cancellation reference by coupling a portion of the transmitter output. This reference signal is then processed through digital signal processing to generate an anti-phase signal that cancels the interference at the receiver input, transforming the problem of interference into an opportunity for active cancellation without requiring higher isolation components.

Inventive Principle:

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

Solution Approach 2:

The patent introduces a digital signal processing unit as an intermediary between the transmitter and receiver paths. This intermediary processes the coupled transmitter signal through complex multiplication and adaptive filtering to generate a cancellation signal, mediating the interference problem without requiring physical isolation improvements in the duplexer.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If digital domain interference cancellation is implemented, then interference cancellation effectiveness is improved, but device complexity increases

Engineering Contradiction:

Improveinterference cancellation effectivenessVSAvoidsignal processing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the interference cancellation function into distinct digital processing stages: signal coupling, digital complex number multiplication for amplitude/phase adjustment, adaptive filtering, and signal subtraction. This modular segmentation allows each function to be implemented independently and optimized separately, managing overall system complexity while achieving effective interference cancellation.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS8331509B2Method and device for cancelling transmitter interference in transceiver, and transceiver

Publication Date: 2012.12.11 HUAWEI TECH CO LTD

AI summary

A method and a device for cancelling transmitter interference in a transceiver, and a transceiver are provided. The method includes: coupling a part of radio frequency signals output from a transmitter, performing amplification, frequency conversion, analog-digital conversion, and digital filtration on the coupled signal by an interference receiver, and outputting a digital signal; performing adaptive equalization on the digital signal output from the interference receiver, and delaying predetermined time of the digital signal output from a receiver, and subtracting the equalized digital signal from the delayed digital signal.