Dual-Path Amplifier Calibration for Phase Mismatch and DC Offset
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Solution Overview
Problem
Existing signal processing methods for amplifiers, particularly in personal audio devices, face challenges in accurately calibrating gain due to phase mismatches and DC offsets between signal paths, leading to inaccurate gain calibration.
Innovation Solution
A method is developed to determine phase misalignment by approximating zero crossing times of signals and applying time-based weighting functions to calculate relative gain, while using correlation functions to minimize the impact of DC offsets, thereby ensuring accurate gain compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single PWM amplifier circuit is used in open-loop or closed-loop mode, then device complexity is reduced, but gain calibration accuracy deteriorates due to phase mismatches and DC offsets between signal paths
Solution Approach 1:
The patent changes the parameters of gain calibration by applying time-based weighting functions to the calibration signals. Instead of using uniform weighting, the system applies weights that emphasize time regions less sensitive to phase mismatches and DC offsets, thereby improving calibration accuracy while maintaining the simple single-amplifier architecture
Solution Approach 2:
The patent uses correlation functions to compare the calibration signal with a reference signal, effectively creating a digital copy for comparison. This allows the system to identify and compensate for phase mismatches and DC offsets by analyzing the correlation between the original and reference signals, improving measurement precision without adding hardware complexity
2Ease of operation
If traditional gain calibration methods are used, then calibration process is simple, but calibration accuracy deteriorates due to sensitivity to phase mismatches and DC offsets
Solution Approach 1:
The patent replaces traditional mechanical or manual calibration adjustment methods with signal processing techniques. By using correlation functions and time-based weighting applied to digital signals, the system achieves accurate gain calibration through computational methods rather than physical adjustments, maintaining ease of operation while improving precision
Solution Approach 2:
The patent introduces correlation functions and time-based weighting functions as intermediary processing steps between the raw calibration signals and the final gain calibration result. These intermediaries filter out the harmful effects of phase mismatches and DC offsets, allowing accurate calibration without complicating the overall process
Data Source
AI summary
A method of determining a phase misalignment between a first signal generated from a first signal path and a second signal generated from a second signal path may include obtaining multiple samples of the first signal proximate to when the first signal crosses zero wherein the first signal can be approximated as linear; obtaining multiple samples of the second signal proximate to when the second signal crosses zero wherein the first signal can be approximated as linear; based on the multiple samples of the first signal, approximating a first time at which the first signal crosses zero; based on the multiple samples of the second signal, approximating a second time at which the second signal crosses zero; and determining the phase misalignment between the first signal and the second signal based on a difference between the first time and the second time.