Phase Delay Extraction in PGC Phase Demodulation
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Solution Overview
Problem
Existing phase demodulation technologies in PGC phase demodulation face challenges in accurately measuring phase delay and compensating for non-linear errors caused by phase delay, especially in sinusoidal modulation interferometers, leading to limited phase measurement accuracy and failure in calculating phase at specific phase delay angles.
Innovation Solution
A method involving band-pass filtering and analog-to-digital conversion of sinusoidal phase modulation interference signals, followed by orthogonal down-mixing and low-pass filtering to extract phase delay using first-order, second-order, and fourth-order orthogonal harmonic amplitude signals, and calculating phase delay correction coefficients to reconstruct harmonic amplitude signals unaffected by phase delay, enabling real-time phase delay compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase delay is adjusted to zero to achieve phase delay compensation, then phase measurement accuracy is improved, but real-time compensation is difficult due to phase delay drift
Solution Approach 1:
The patent implements real-time phase delay compensation by extracting phase delay information from harmonic amplitude signals and using this information to dynamically correct the phase measurement. The system continuously monitors the phase delay through the relationship between first-order and second-order harmonic amplitude signals and applies real-time correction, creating a closed-loop feedback mechanism that maintains measurement accuracy despite phase delay drift.
Solution Approach 2:
The system uses the harmonic amplitude signals already present in the interference signal to extract phase delay information without requiring external calibration or adjustment mechanisms. The phase delay compensation is achieved using the signal's own characteristics, eliminating the need for separate phase delay adjustment devices or procedures.
2Measurement precision
If phase delay deviates from zero, then non-linear error occurs limiting phase measurement accuracy, but existing methods cannot achieve real-time compensation
Solution Approach 1:
The patent establishes a real-time feedback mechanism where phase delay is continuously extracted from the ratio of first-order to second-order harmonic amplitude signals, and this extracted phase delay is immediately used to correct measurement errors. This dynamic feedback approach ensures stable compensation even when phase delay deviates from zero, maintaining both accuracy and reliability.
Solution Approach 2:
The system performs preliminary extraction of phase delay information from harmonic amplitude signals before the actual phase measurement is completed. By obtaining the phase delay value in advance through the relationship between different order harmonic signals, the system can pre-calculate the necessary correction and apply it to eliminate non-linear errors before they affect the final measurement result.
3Productivity
If phase delay equals specific angle, then harmonic amplitude signals become zero causing PGC-DCM and PGC-Arctan algorithms to fail
Solution Approach 1:
The patent introduces a new phase extraction method that uses the relationship between first-order and second-order harmonic amplitude signals as an intermediary to determine phase delay. Instead of relying on algorithms that fail when harmonic signals become zero, the system uses the ratio and relationship between different order harmonics to extract phase information, providing a reliable alternative that works across all phase delay angles.
Solution Approach 2:
The system changes the parameter used for phase delay extraction from single harmonic amplitude to the relationship between multiple harmonic orders. By utilizing the ratio and phase relationship between first-order and second-order harmonic amplitude signals, the system transforms the measurement approach to one that remains valid even when individual harmonic components become zero at specific phase delay angles.
Data Source
AI summary
The disclosure discloses a phase delay extraction and compensation method in a PGC phase demodulation technology. The sinusoidal phase modulation interference signal is converted into a digital interference signal by an analog-to-digital converter after amplification and filtering, and the digital interference signal is subjected to orthogonal downmixing of first-order, second-order, and fourth-order harmonics simultaneously to obtain three pairs of orthogonal harmonic amplitude signals. The three pairs of orthogonal harmonic amplitude signals are used to extract phase delay, and the result is used to calculate the corresponding phase delay correction coefficients, and the phase delay correction coefficient are multiplied by the corresponding absolute harmonic amplitude signal equal to the sum of the absolute value of the orthogonal harmonic amplitude signals to obtain a new harmonic amplitude signal that is not affected by the phase delay, then the phase to be measured is obtained through the arc tangent operation.