Transceiver Interference Tolerance via Distortion Estimation

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Solution Overview

Problem

Homodyne and low-IF receivers are susceptible to interference from transmitter leakage signals due to limited stop-band attenuation in duplexing filters, leading to distortion effects in the receiver's mixer stage, which complicates filtering requirements and increases device size and cost.

Innovation Solution

The implementation of a distortion estimation unit that approximates non-linear response characteristics of the downconverter circuit to generate a distortion signal estimate, which is then filtered and combined with the desired signal in an interference subtraction unit to reduce interference, allowing for simplified filtering and improved tolerance to transmitter leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of moving object

If homodyne or low-IF receivers are used to reduce the number of tuned circuits, then device integration and size are improved, but susceptibility to transmitter leakage interference increases

Engineering Contradiction:

Improvereceiver sizeVSAvoidtransmitter leakage interference

Core Design Contradiction:

Volume of moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent uses the transmitter signal itself, after applying a non-linear function, to generate an interference estimate that is then subtracted from the received signal. This converts the harmful transmitter leakage into a useful cancellation signal, allowing the receiver to tolerate the interference without requiring additional filtering hardware.

Inventive Principle:

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

Solution Approach 2:

The patent introduces an intermediary processing stage that includes a non-linear function generator and an interference subtraction unit. These intermediary components process the transmitter signal to create a cancelled interference signal, which then combines with the received signal to eliminate the harmful interference effect.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If duplexing filters with limited stop-band attenuation are used, then device complexity is reduced, but transmitter leakage through the filter increases

Engineering Contradiction:

Improvefiltering complexityVSAvoidtransmitter leakage signal

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

Instead of relying on filters to block transmitter leakage, the patent uses the leaked signal itself (processed through a non-linear function) to generate an interference estimate that is subtracted from the received signal. This converts the leakage problem into a solvable signal processing task.

Inventive Principle:

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

Solution Approach 2:

The patent replaces the mechanical/filter-based approach to blocking interference with a digital signal processing approach. Instead of using more complex filters to block transmitter leakage, the system uses non-linear signal processing and subtraction to eliminate the interference electronically.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Object-affected harmful factors

If additional filters are added to suppress transmitter leakage, then interference rejection is improved, but device size and cost increase

Engineering Contradiction:

Improvetransmitter leakage interferenceVSAvoidnumber of filters

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent turns the transmitter leakage signal into a useful resource by using it to generate an interference estimate. This estimated interference is then subtracted from the received signal, effectively canceling the leakage without requiring additional filters.

Inventive Principle:

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

Solution Approach 2:

The patent creates a copy of the transmitter signal (the interference estimate) by applying a non-linear function to it. This copy is then used to cancel the original interference in the received signal, avoiding the need for additional filtering hardware.

Inventive Principle:

Principle #26Copying

Data Source

PatentUS7995973B2Own transmitter interference tolerant transceiver and receiving methods

Publication Date: 2011.08.09 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Circuits and methods are disclosed for reducing interference from transmitter leakage in a radio transceiver. An exemplary method for reducing interference from transmitter leakage in a radio transceiver comprises downconverting, filtering, and sampling a radio frequency signal comprising a desired signal and a transmitter leakage signal to obtain a sampled signal of interest. The method further comprises generating a sampled distortion signal estimate that estimates one or more distortion products of the transmitter leakage signal, such as a squared amplitude obtained from a square-law device or corresponding digital function. Further, the method comprises dividing the sampled distortion signal estimate and the sampled signal of interest into a plurality of frequency channels. Finally, for a selected number of frequency channels, the method comprises combining the sampled distortion signal estimate for a frequency channel with the corresponding sampled signal of interest for the same frequency channel to obtain interference-reduced signal samples for the frequency channel.