SAR Backscatter Array Calibration for Resolution-Cell Signal Processing
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Solution Overview
Problem
Existing synthetic aperture radar (SAR) calibration methods face challenges with passive angle reflectors that are difficult to manufacture and install for longer-wavelength radar radiation, and active transponders have limited parameter influence, necessitating improved methods for generating SAR raw data adapted to downstream signal processing.
Innovation Solution
A synthetic aperture radar method and system that utilizes backscatter arrays with predetermined patterns of passive and active elements, allowing for precise backscatter parameter incorporation into signal processing, enabling geometric, radiometric, and polarimetric calibration of SAR images.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individually set up passive angle reflectors (corner reflectors) are used for calibration, then backscatter parameters can be obtained, but the reflectors have to have very large dimensions for longer-wave radar radiation, making them difficult to manufacture and set up
Solution Approach 1:
The invention divides a single large corner reflector into multiple smaller corner reflectors arranged in an array. Each small corner reflector has dimensions suitable for manufacturing and setup, while the collective array provides the equivalent calibration effect of a large reflector. The resolution cell encompasses multiple these small reflectors, allowing SAR raw data to be generated that is adapted to signal processing requirements.
2Adaptability or versatility
If active transponders are used as backscatter elements, then backscatter parameters can be influenced, but the influence is limited within certain bounds
Solution Approach 1:
The invention uses multiple small corner reflectors with different orientations and positions within the resolution cell, each contributing different backscatter characteristics. By selectively activating or deactivating specific reflectors in the array, precise control over the overall backscatter parameters is achieved, overcoming the limited adjustability of single active transponders.
3Adaptability or versatility
If SAR raw data are generated using conventional methods, then general remote sensing is possible, but the data are not specifically adapted to downstream signal processing needs
Solution Approach 1:
The invention performs preliminary arrangement of corner reflectors in specific patterns within resolution cells before SAR data acquisition. This pre-configuration ensures that the raw SAR data inherently contains the necessary calibration information and is specifically adapted for downstream signal processing tasks such as radiometric calibration, geometric calibration, and polarimetric calibration, eliminating the need for separate calibration procedures.
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
Enables efficient calibration and enhanced signal processing of SAR images, facilitating accurate geographic location assignment, radiometric comparison, and polarimetric differentiation, as well as orbit determination and target identification.
Implementation Method 1
a radar device which moves in an azimuth direction over the earth's surface, the radar device comprising a transmitting device for transmitting radar pulses and a receiving device for receiving radar echoes
Implementation Method 2
passive backscatter elements that generate the radar echoes purely through reflection
Implementation Method 3
active backscatter elements in the form of so-called transponders, which actively emit a corresponding radar echo in response to a received radar signal
Data Source
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AI summary
The invention relates to a synthetic-aperture radar method for remote sensing of the earth's surface by means of a radar device (1), which is moved across the earth's surface in an azimuth direction (x), wherein the radar device (1) comprises a transmitting device for emitting radar pulses and a receiving device for receiving radar echoes. In a defined operating mode of the radar device (1), radar pulses are emitted by the transmitting device and radar echos are received by the receiving device, wherein, for the defined operating mode, resolution cells are defined, which are area segments on the earth's surface having identical dimensions and which represent the spatial resolution of the defined operating mode. Furthermore, in the defined operating mode, raw SAR data are captured by the receipt of radar echos that originate from one or more backscattering arrangements (2) installed on the earth's surface, each composed of a plurality of backscattering elements (3), wherein the backscattering elements (3) of each backscattering arrangement (2) are position relative to each other in such a way that all backscattering elements (3) of the backscattering arrangement (2) lie within one resolution cell, and wherein each backscattering arrangement (2) has one or more backscattering parameters known in advance. The raw SAR data are subjected to signal processing, which comprises the production of SAR radar images of the earth's surface from the raw SAR data and which is dependent on the one or more backscattering parameters known in advance.