SODAR Doppler Error Correction via Chirp Differencing
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Solution Overview
Problem
SODAR systems using wideband acoustic chirps face systematic Doppler errors in wind speed and direction measurements, leading to excessive resolution and height errors due to wind speed displacement on opposite beams.
Innovation Solution
The method involves transmitting forward and reverse acoustic chirps in opposite directions to correct Doppler-induced wind speed range errors by differencing the acoustic echoes received from these chirps, ensuring range errors are in the same direction, which can be halved and removed by shifting wind speed data to a new height based on Doppler measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wideband acoustic chirps are used in SODAR systems to achieve pulse compression, then gain and resolution are improved, but systematic Doppler errors are introduced into wind speed and direction measurements
Solution Approach 1:
The patent applies preliminary anti-action by transmitting acoustic chirps in both forward and reverse directions before processing. This allows the system to preemptively capture Doppler errors in both directions, then cancel them out through differencing operations, thereby preventing the systematic errors from affecting the final wind speed measurement
Solution Approach 2:
The patent converts the harmful Doppler errors into a beneficial measurement technique. By intentionally measuring Doppler shifts in both forward and reverse directions, the system transforms the error source into a useful signal that, when differenced, reveals the true wind speed while eliminating the systematic errors
2Measurement precision
If forward and reverse acoustic chirps are transmitted in opposite directions, then Doppler errors can be corrected through differencing, but the system complexity increases
Solution Approach 1:
The patent merges the forward and reverse chirp transmission systems into a unified measurement approach. By combining the measurements from both directions and processing them through differencing, the system achieves error correction while maintaining a relatively simple overall architecture that leverages existing SODAR components
3Area of stationary object
If multiple receivers are used to detect echoes from transmitted chirps, then measurement coverage is improved, but Doppler errors in wind speed and direction measurements increase
Solution Approach 1:
The patent segments the measurement process by assigning different reception directions (forward and reverse) to different receivers or receiver configurations. This segmentation allows each receiver to measure Doppler shifts in its specific direction, which are then combined through differencing to eliminate systematic errors while maintaining broad measurement coverage
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 systematic Doppler errors in SODAR systems, improving the accuracy of wind speed and direction measurements by aligning range errors for opposite beams, thereby enhancing the precision of wind shear profiles.
Implementation Method 1
transmitting forward and reverse acoustic chirps in opposite directions
Implementation Method 2
receiving one or more acoustic echoes of the transmitted chirps
Implementation Method 3
reflection, refraction and/or scattering of the transmitted chirp
Implementation Method 4
correcting Doppler induced wind speed range errors... differencing the acoustic echoes received from these chirps... based on Doppler measurements
Data Source
AI summary
This invention relates to a method of reducing error in a SODAR system adapted to locate discontinuities in the atmosphere over a range extending away from an acoustic transmitter and receiver, the method comprising the steps of: measuring wind to determine either a substantially upwind direction or a substantially downwind direction relative to the transmitter; transmitting one or more forward or reverse acoustic chirps in the substantially upwind or downwind direction; receiving one or more acoustic echoes of the transmitted chirps; and processing the acoustic echoes to provide an indication of the discontinuities in the atmosphere over the range, thereby providing a wind shear profile.