Wireless Transceiver IQ Imbalance Calibration via Spectrum Analysis
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Solution Overview
Problem
High-level Quadrature Amplitude Modulation (QAM) communication systems face performance degradation due to In-phase Quadrature-phase (IQ) imbalance, leading to poor Bit Error Rate (BER) and image signal generation, which existing calibration methods struggle to address effectively across varying conditions such as temperature and amplifier variations.
Innovation Solution
A calibration method and apparatus for wireless transceivers that involve generating a test signal, configuring calibration coefficients, and performing spectrum analysis to adjust these coefficients, ensuring optimal IQ balance between the in-phase and quadrature-phase paths, even in the presence of temperature and amplifier variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-level Quadrature Amplitude Modulation (QAM) is adopted to increase transmission rate, then transmission rate is improved, but IQ imbalance causes performance degradation and poor Bit Error Rate
Solution Approach 1:
The patent performs IQ calibration before formal signal transmission by injecting a calibration signal and adjusting calibration coefficients to compensate for IQ imbalance. This preliminary action corrects the mismatch between in-phase and quadrature-phase paths before actual data transmission, ensuring optimal performance for high-level QAM modulation.
Solution Approach 2:
The patent implements a feedback mechanism where the receiver measures the calibration signal, calculates IQ imbalance parameters, and feeds back calibration coefficients to the transmitter. This closed-loop feedback enables continuous optimization of IQ balance, maintaining low Bit Error Rate even under varying channel conditions.
2Manufacturing precision
If calibration process is performed to improve IQ balance, then IQ imbalance is reduced, but calibration complexity and measurement requirements increase
Solution Approach 1:
The patent extracts the calibration function into a separate, dedicated process that uses a specific calibration signal independent of data transmission. By separating calibration from normal operation and using a dedicated calibration signal, the system simplifies the calibration process while achieving precise IQ balance adjustment through dedicated calibration coefficients.
Solution Approach 2:
The patent adjusts calibration coefficients as variable parameters to compensate for IQ imbalance. By changing these coefficients based on measured imbalance characteristics, the system achieves precise IQ balance adjustment without modifying the fundamental transmitter structure, thereby reducing calibration complexity.
3Object-generated harmful factors
If calibration coefficients are adjusted to compensate for IQ mismatch, then image signal ratio is improved, but calibration time and measurement precision requirements increase
Solution Approach 1:
The patent performs spectrum analysis on the calibration signal before formal transmission to determine IQ imbalance characteristics. This preliminary measurement allows the system to calculate appropriate calibration coefficients that will maximize image signal ratio, reducing the need for high-precision measurements during actual data transmission.
Data Source
AI summary
A calibration method for calibrating a communication system includes: generating a test signal at a transmitter; configuring at least one calibration coefficient at the transmitter; configuring at least one calibration coefficient at the receiver; transmitting the test signal to a receiver via the calibration coefficient; performing a spectrum analysis upon the test signal received by the receiver to generate a spectrum analysis result; and adjusting the calibration coefficient according to the spectrum analysis result to calibrate the transmitter. In addition, a calibration method is also provided for calibrating a receiver of a communication system, and related calibration apparatuses are further provided.