Laser Radar Frequency Shift Correction for Molecular Concentration
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Solution Overview
Problem
Conventional laser radar devices experience a deterioration in calculation accuracy of molecular concentration when the position of scattering bodies in the atmosphere changes due to wind speed or direction, leading to a Doppler shift that affects the signal-to-noise ratio and peak intensity identification.
Innovation Solution
The implementation of a laser radar device with a spectrum calculating unit, frequency shift correcting unit, and spectrum integrating unit to correct frequency shifts and integrate signal spectra, ensuring accurate molecular concentration calculation even with changing scattering body positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal spectra are integrated to increase signal-to-noise ratio, then measurement precision improves when scattering bodies are stationary, but calculation accuracy deteriorates when scattering bodies move due to Doppler shift
Solution Approach 1:
The frequency shift correcting unit performs preliminary correction of Doppler shifts in signal spectra before integration. By pre-adjusting frequency positions to account for expected Doppler effects caused by wind-driven scattering body movement, the integration process can then accurately combine signal components without cancellation errors, maintaining both high signal-to-noise ratio and calculation accuracy.
Solution Approach 2:
The system dynamically adjusts frequency parameters by detecting and correcting Doppler shifts in real-time. The frequency shift correcting unit modifies frequency positions of signal spectra based on detected Doppler effects, allowing the integration process to maintain accuracy despite changing atmospheric conditions and scattering body movements.
2Reliability
If frequency shift correction is applied to moving scattering bodies, then calculation accuracy is maintained, but device complexity increases
Solution Approach 1:
The frequency shift correcting unit implements a feedback mechanism where Doppler shifts are detected from the signal spectra themselves, and correction amounts are automatically determined and applied. This self-regulating approach maintains calculation accuracy without requiring complex external control systems or manual intervention.
Solution Approach 2:
The signal processing system performs its own frequency shift correction using information extracted from the received signal spectra. By utilizing the spectral data already present in the received signals, the system self-corrects Doppler effects without requiring additional separate measurement systems or complex external processing equipment.
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 configuration prevents the deterioration of molecular concentration calculation accuracy by correcting frequency shifts and integrating signal spectra, maintaining high accuracy despite changes in the scattering body's position within the atmosphere.
Implementation Method 1
receives scattered light of the laser light of the absorption wavelength and scattered light of the laser light of the non-absorption wavelength that are scattered by aerosol in the atmosphere
Implementation Method 2
an optical coupler which combines the absorption wavelength scattered light received by the optical antenna and the laser light of the absorption wavelength and combines the non-absorption wavelength scattered light received by the optical antenna and the laser light of the non-absorption wavelength
Implementation Method 3
an optical receiver which detects the absorption wavelength combined light beam output from the optical coupler and outputs a reception signal of the absorption wavelength combined light beam
Implementation Method 4
the signal processor calculates a plurality of signal spectra of the absorption wavelength combined light beam for each time range by performing fast Fourier transform on the reception signal of the absorption wavelength combined light beam
Implementation Method 5
The signal processor integrates a plurality of signal spectra by integrating signal components of the same frequency in a plurality of signal spectra within the same time range in order to increase a signal-to-noise ratio (SN ratio)
Implementation Method 6
one of which generates laser light at an absorption wavelength which is a wavelength absorbed by the molecule in the atmosphere, another of which generates laser light at a non-absorption wavelength which is a wavelength not absorbed by the molecule in the atmosphere
Data Source
AI summary
A frequency shift correcting unit (25) which corrects a frequency shift of a plurality of first signal spectra within the same time range with respect to a frequency of first laser light beam and corrects a frequency shift of a plurality of second signal spectra within the same time range with respect to a frequency of second laser light beam, and a spectrum integrating unit (26) which integrates a plurality of first signal spectra corrected by the frequency shift correcting unit (25) and integrates a plurality of second signal spectra corrected by the frequency shift correcting unit (25) are provided, and a molecular concentration calculating unit (27) calculates a concentration of molecules in the atmosphere from the first and second signal spectra integrated by the spectrum calculating unit (26).