I/Q Imbalance Compensation Using Single-Tone Filter Coefficients

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Solution Overview

Problem

Wireless communication systems suffer from signal imbalance, specifically I/Q imbalance, due to phase and amplitude mismatches between in-phase and quadrature signals, caused by local oscillators and mismatches in analog elements, leading to interference and noise.

Innovation Solution

A method that involves generating filter coefficients by processing single-tone signals in both the transmitter and receiver, transforming them into frequency domains, and applying inverse Fast Fourier Transform to obtain time-domain coefficients, which are then used to generate compensation signals to neutralize the I/Q imbalance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If local oscillator signals are used in mixers to process quadrature and in-phase signals, then signal mixing and frequency conversion are achieved, but I/Q imbalance occurs causing interference and noise

Engineering Contradiction:

Improvesignal mixing capabilityVSAvoidI/Q imbalance interference

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by generating compensation signals before the main signal processing occurs. The method pre-calculates filter coefficients based on channel state information and generates compensation signals that are then applied to the received signal to counteract the I/Q imbalance that will occur during normal operation. This proactive approach prevents the interference from degrading signal quality.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent converts the harmful I/Q imbalance effect into a beneficial compensation mechanism. By analyzing the channel state information and the specific characteristics of the I/Q imbalance, the system generates compensation signals that utilize the known imbalance characteristics to create corrective signals. The harmful interference pattern is transformed into useful information for generating the compensation algorithm.

Inventive Principle:

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

2Reliability

If filter coefficients are generated and compensation signals are applied to neutralize I/Q imbalance, then signal orthogonality is preserved and interference is reduced, but additional processing steps and computational complexity are introduced

Engineering Contradiction:

Improvesignal orthogonalityVSAvoidprocessing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent implements feedback by continuously monitoring channel state information and using this information to generate updated compensation signals. The system receives feedback about the channel conditions and the effect of previous compensation applications, then adjusts the filter coefficients and compensation signals accordingly. This closed-loop approach ensures that the compensation remains effective as channel conditions change, while the feedback mechanism provides a systematic way to manage the complexity.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8831550B2Method of compensating signal imbalance of wireless communication system

Publication Date: 2014.09.09 REALTEK SEMICON CORP

AI summary

Filter coefficients are generated by testing a wireless communication system using single-tone signals. While using the filter coefficients in a filter module, signal imbalance caused by a local oscillator or analog elements in a wireless communication system can be eliminated, so as to prevent the wireless communication system from being affected by the noises.