RF I/Q Path Calibration for DC Offset and LO Leakage Control

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Solution Overview

Problem

Radio frequency (RF) circuits in wireless devices often encounter in-phase quadrature-phase imbalance (IQ imbalance), leading to leakage of local oscillator (LO) signals due to unmatched direct current (DC) offsets.

Innovation Solution

A calibration method for RF circuits that includes calibrating DC offsets of modulators and components, swapping the in-phase and quadrature-phase paths, and setting digital-to-analog converter (IDAC) values based on target setting values to achieve balanced DC offsets and reduce LO signal leakage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If DC offset calibration is performed without swapping I-path and Q-path, then calibration process is simple, but IQ imbalance cannot be effectively corrected

Engineering Contradiction:
ImproveIQ imbalance correction accuracyVSAvoidcalibration process complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by performing DC offset calibration on the I-path first, then swapping the I-path and Q-path to perform calibration on the Q-path. This preliminary calibration sequence ensures that both paths are calibrated with reference to a common baseline, improving IQ imbalance correction accuracy while maintaining a systematic and manageable calibration process.

Inventive Principle:
Principle #10Preliminary action

2Manufacturing precision

If multiple calibration steps are performed to improve IQ imbalance correction, then calibration accuracy is improved, but calibration time increases

Engineering Contradiction:
ImproveDC offset calibration accuracyVSAvoidcalibration time
Core Design Contradiction:
Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent applies periodic action by performing calibration in distinct periodic phases: first calibrating the I-path DC offset, then swapping paths and calibrating the Q-path DC offset, followed by second-stage calibrations. This periodic structure allows thorough calibration of both paths while organizing the process into manageable cycles, balancing accuracy requirements with time efficiency.

Inventive Principle:
Principle #19Periodic action

Data Source

PatentUS12309018B2Radio frequency circuit and calibration method therefor
Publication Date: 2025.05.20 REALTEK SEMICON CORP
  • US12309018B2 patent drawing
  • US12309018B2 patent drawing
  • US12309018B2 patent drawing

AI summary

A method of calibrating a radio frequency (RF) circuit that includes an in-phase path (I-path) and a quadrature-phase path (Q-path) is provided. The I-path includes a first modulator and a first component, and the Q-path includes a second modulator and a second component. The modulators and the components respectively include a current DAC (IDAC). The calibration method includes: calibrating DC offsets of the first and second modulators to obtain a first setting value; swapping the I-path and the Q-path, and calibrating DC offsets of the first and second modulators again to obtain a second setting value; setting the IDACs of the first and second modulators with a value of a function of the first and second setting values; calibrating DC offsets of the first and second components; calibrating DC offsets of the first and second modulators; and calibrating DC offsets of the first and second components.