SAR Raw Data Calibration Without Image Formation
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Solution Overview
Problem
Conventional SAR sensor calibration methods are complex and require SAR image formation, making them inefficient and unsuitable for situations where precise calibration is necessary, especially for sensors employing beamforming.
Innovation Solution
A method for computer-assisted processing of SAR raw data that derives calibration factors directly from the raw data without forming images, using known radar cross sections and positions of reference targets to minimize measurement variations, and determines correction terms for sensor parameters to improve image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SAR sensor calibration methods are used, then calibration can be performed, but the process becomes complex and requires SAR image formation
Solution Approach 1:
The patent extracts the calibration process from the image formation process by performing calibration directly on SAR raw data before image formation. This separates the calibration function from the imaging function, allowing calibration to be performed independently without requiring complete image formation, thereby reducing process complexity while maintaining precision
Solution Approach 2:
The patent performs calibration as a preliminary action before image formation by processing SAR raw data to determine calibration factors. This preliminary calibration step prepares the data for subsequent imaging operations, ensuring accurate calibration is achieved before the complex image formation process begins
2Measurement precision
If SAR image formation is performed for calibration, then calibration factors can be determined, but processing time and computational resources increase
Solution Approach 1:
The patent extracts only the essential calibration information from SAR raw data without performing complete image formation. By selecting and processing only the necessary data elements required for calibration factor determination, the method achieves accurate calibration while significantly reducing processing time and computational resource requirements
Solution Approach 2:
The patent applies partial action by performing only the minimal necessary processing on SAR raw data to obtain calibration factors, rather than completing full image formation. This partial processing approach focuses computational effort solely on extracting calibration parameters, reducing overall processing time while maintaining calibration accuracy
3Reliability
If conventional calibration methods are used, then calibration can be achieved, but efficiency is reduced due to required image formation
Solution Approach 1:
The patent extracts the calibration function from the image formation workflow by implementing a dedicated calibration process that operates directly on SAR raw data. This extraction enables calibration to be performed independently and more efficiently, improving productivity while maintaining the reliability needed for accurate sensor calibration
Solution Approach 2:
The patent performs calibration as a preliminary action before image formation, ensuring reliable calibration factors are determined in advance. This preliminary calibration step improves overall workflow efficiency by preparing data for imaging operations without requiring time-consuming post-processing calibration steps
Data Source
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AI summary
The invention refers to a method for computer-assisted processing of SAR raw data (Dpq), comprising radar echoes from ground that are the response to radar pulses (RP) that have been transmitted by antenna elements (101, 102, 103) of a radar sensor (1) on at least one flying object (SA) moving in an azimuth direction (x) above ground and where the radar echoes have been received by antenna elements (101, 102, 103) of the radar sensor (1), the SAR raw data (Dpq) including radar echoes originating from reference targets (RT) with known radar cross sections and positions on ground and being represented by data acquisitions for several channels (pq), each channel (pq) referring to radar pulses transmitted by a specific antenna element (101, 102, 103) and radar echoes received by a specific antenna element (101, 102, 103). The method comprises one or more calibration procedures (TA2, S2; TA3, S3; TA4, S4), each calibration procedure comprising the following steps: i) by using the known radar cross section and position on ground for each reference target (RT), extracting target data (Fspq) for each reference target (RT) in each channel (pq) from the SAR raw data (Dpq) and determining a variation of one or more measurements (δφspq, δRCSspq, δφspq,uv) over different radar echoes originating from each reference target (RT) for each channel (pq) or for each combination of two channels (pq) based on the target data (Fspq); ii) determining one or more calibration factors in the form of one or more correction terms (ΔAe, ΔLe, ΔLeinf) for one or more sensor parameters of the radar sensor (1) based on an optimisation comprising the optimisation goal to minimise the variation of the one or more measurements (δφspq, δRCSspq, δφspq,uv) for all reference targets (RT) and for all channels (pq) or all combinations of two channels (pq).