Direct-Conversion Receiver Circuit for I/Q Mismatch Mitigation

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Solution Overview

Problem

Direct conversion receivers (DCRs) face performance degradation due to In-Phase/Quadrature (I/Q) mismatch issues caused by gain and phase errors in analog implementations, leading to signal corruption and noise ratio distortion.

Innovation Solution

The proposed electrical circuit architecture includes a local oscillator generating reference signals with specific phase shifts, mixers, low pass filters, and correcting filters to mitigate I/Q mismatches by adjusting filter coefficients and applying gain corrections, minimizing power dissipation and external components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If DCR architecture is used to reduce complexity and power dissipation, then power consumption and device complexity are reduced, but I/Q mismatch and signal quality deteriorate

Engineering Contradiction:

Improvepower dissipationVSAvoidsignal quality

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent implements feedback by using the output signal to adjust and correct the I/Q mismatch parameters. The system continuously monitors the received signal and adjusts the correction filters and gain/phase balancers to minimize I/Q imbalance, thereby maintaining signal quality while using the efficient DCR architecture.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent dynamically changes parameters such as filter coefficients, gain factors, and phase shifts to compensate for I/Q mismatch. By adjusting these parameters based on measured signal characteristics, the system maintains optimal performance without requiring complex hardware modifications.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If correction filters and gain adjustments are added to mitigate I/Q mismatch, then signal quality improves, but device complexity increases

Engineering Contradiction:

Improvesignal qualityVSAvoidcircuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent makes existing DCR components multi-functional by having them perform both their primary signal processing functions and additional I/Q correction functions. The correction filters are integrated into the existing signal path, and the same hardware blocks are used for both reception and mismatch compensation, avoiding the need for separate dedicated correction circuits.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If precise filter coefficients and gain corrections are applied, then I/Q mismatch is reduced, but manufacturing precision requirements increase

Engineering Contradiction:

ImproveI/Q mismatch mitigationVSAvoidfilter coefficient precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent performs preliminary calibration and measurement during the manufacturing process to determine the specific I/Q mismatch characteristics of each device. These pre-determined correction parameters are then stored and applied during operation, eliminating the need for high manufacturing precision by compensating for variations after production.

Inventive Principle:

Principle #10Preliminary action

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 approach effectively reduces channel impulse response mismatches and phase errors, enhancing signal quality and noise ratio by configuring equivalent filter coefficients and applying gain corrections, thereby improving the performance of DCRs.

Implementation Method 1

a local oscillator configured to generate a first reference signal and a second reference signal having a predetermined phase shift with the first reference signal

Methodology Applied

Scientific EffectPhase shift:

Implementation Method 2

a mixer configured to multiply two input signals to generate a third output signal

Methodology Applied

Scientific EffectMixing:

Implementation Method 3

a first low pass filter configured to approximately attenuate frequencies in the second output to generate a third output

Methodology Applied

Scientific EffectFiltering: Filter (electronic)

Data Source

PatentUS8948326B2Circuit architecture for I/Q mismatch mitigation in direct conversion receivers

Publication Date: 2015.02.03 ANALOG DEVICES INT UNLTD CO

AI summary

An electrical circuit includes a local oscillator configured to generate a first reference signal and a second reference signal having a predetermined phase shift with the first reference signal, an I-channel mixer configured to inject the first reference signal to an incoming signal and generate a first output, a compensation mixer configured to multiply the first output with a constant factor to generate a second output, a first low pass filter configured to approximately attenuate frequencies in the second output to generate a third output, and a first correcting filter configured to filter the third output to generate a fourth output. The first correcting filter is configured to reduce a channel impulse response mismatch between the first low pass filter and a second low pass filter, which is configured to attenuate frequencies in a Q-channel of the incoming signal. In specific embodiments, the phase shift includes 45°.