IQ Signal Path Calibration Using Test Signal Spectrum Analysis
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Solution Overview
Problem
Existing communication systems face challenges in quickly and accurately calibrating in-phase (I) and quadrature (Q) signal path mismatches, leading to increased Bit Error Rate (BER) due to IQ imbalance, which affects the Error Vector Magnitude (EVM) and signal quality, especially in high modulation schemes like 64-QAM or 256-QAM.
Innovation Solution
A calibration method and apparatus that utilize a test signal to perform spectrum analysis and calculate calibration coefficients to compensate for mismatches between the I and Q signal paths, enabling faster and more accurate calibration of amplitude and phase mismatches, thereby reducing image interference and improving communication performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the searching method is used to approximate the optimal compensating value gradually, then the calibration accuracy can be improved, but the calibration speed becomes slow
Solution Approach 1:
The patent applies preliminary action by using a test signal to pre-calibrate the signal paths before actual communication begins. The calibration process is performed in advance using known test signals, allowing the system to achieve accurate calibration without slow gradual searching during operational mode. This pre-computation of calibration values enables fast and accurate calibration overall.
2Productivity
If higher modulation schemes like 64-QAM or 256-QAM are used, then the transmission rate can be increased, but the requirement for low EVM and high signal quality becomes more stringent
Solution Approach 1:
The patent performs IQ imbalance calibration in advance using test signals before actual high-rate communication begins. By pre-establishing accurate calibration coefficients for the I and Q signal paths, the system ensures low EVM and high signal quality are achieved from the start of operational mode, enabling reliable higher modulation schemes without quality degradation.
3Ease of manufacture
If IQ imbalance exists in the signal paths, then circuit implementation is simplified, but image interference appears and reduces signal quality
Solution Approach 1:
The patent implements feedback by using the received test signal to measure the actual IQ imbalance in the signal paths. The calibration coefficient calculating unit processes the test signal to determine the degree of mismatch between I and Q paths, then calculates appropriate calibration coefficients to compensate for the imbalance. This feedback mechanism allows the system to maintain simple circuit implementation while actively correcting image interference through calculated compensation.
Data Source
AI summary
A method for calibrating mismatches of an in-phase signal path and a quadrature signal path of a receiver is proposed in the present invention, including: utilizing the receiver to receive at least one test signal with a specific frequency via the first signal path and the second signal path, to generate a first signal path received signal and a second signal path received signal; performing frequency analysis upon the first signal path received signal and the second signal path received signal respectively, to generate a first frequency analysis result and a second frequency analysis result; and calculating at least one calibration coefficient according to the first frequency analysis result and the second frequency analysis result. A method for calibrating mismatches of an in-phase signal path and a quadrature signal path of a transmitter is also proposed in the present invention.