RFOG Modulation Amplitude Adjuster for Harmonic Distortion
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Solution Overview
Problem
Resonator fiber optic gyroscopes (RFOGs) face accuracy degradation due to 2nd order harmonic distortion, which amplifies rotational errors and diminishes measurement precision.
Innovation Solution
A modulation amplitude adjuster is used to amplify the modulation signal by a factor representing the square root of the ratio of constants, minimizing total harmonic distortion by injecting a suitably amplified sinusoidal signal to suppress 2nd order harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the modulation amplitude is increased to maximize sensitivity to laser frequency deviations, then the sensitivity of the resonator output to frequency deviations is improved, but the 2nd order harmonic distortion is amplified causing rotation sensing errors
Solution Approach 1:
The patent applies parameter changes by carefully selecting and adjusting the modulation amplitude to an optimal value that balances sensitivity and distortion. By changing the modulation depth parameter, the system achieves sufficient frequency deviation detection while keeping 2nd order harmonic distortion below threshold levels that would cause rotation sensing errors
Solution Approach 2:
The patent implements feedback by monitoring the resonator output for signs of 2nd order harmonic distortion and automatically adjusting the modulation amplitude accordingly. The system measures the distortion level and reduces modulation amplitude when distortion exceeds acceptable thresholds, thereby eliminating rotation sensing errors while maintaining adequate sensitivity
2Measurement precision
If the modulation amplitude is set to maximize sensitivity, then the detection capability is improved, but rotation sensing errors due to harmonic distortion increase
Solution Approach 1:
The patent changes the modulation amplitude parameter to an optimal value that simultaneously improves rotation sensing accuracy and maintains measurement reliability. By selecting a modulation depth that maximizes the signal-to-noise ratio for rotation detection while staying below distortion-threshold levels, the system achieves both high accuracy and reliable measurements
Solution Approach 2:
The system uses feedback to continuously monitor rotation sensing errors and adjust modulation amplitude in real-time. When distortion-induced errors are detected, the feedback loop reduces modulation amplitude to eliminate the errors, thereby maintaining reliable rotation measurements throughout operation
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces or eliminates 2nd order harmonic distortion, enhancing the accuracy of rotation rate measurements by minimizing rotational sensing errors and maintaining sensitivity to laser frequency deviations.
Implementation Method 1
The beam generating device modulates or shifts the frequencies of each of the counter-propagating light beams so that the resonance frequencies of the resonant coil may be observed
Implementation Method 2
The resonance frequencies for each of the CW and CCW paths through the coil are based on a constructive interference condition such that all light-waves having traversed the coil a different number of times interfere constructively at any point in the coil
Implementation Method 3
A rotation about the axis of the coil produces a different pathlength for clockwise and counterclockwise propagation, thus producing a shift between the respective resonance frequencies of the resonator, and the frequency difference indicates the rotation rate
Data Source
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AI summary
A device and a method for suppressing 2nd order harmonic distortion in a Resonator Fiber Optic Gyroscope includes driving a laser to generate at least one of a plurality of counter propagating laser beams traveling through a fiber optic resonator according to a modulated signal. The modulated signal can be represented by a polynomial having two terms, and each of the two terms is suitably multiplied by a coefficient and a constant. A modulation amplitude adjuster amplifies the modulation signal by an amplification factor as it is used to drive the laser. When the amplification factor is suitably chosen to represent a square root of a ratio of the constants, the total harmonic distortion in the RFOG is minimized.