Subsurface Imaging Radar Clutter Cancellation
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Solution Overview
Problem
Current radar systems face challenges in achieving sufficient resolution and efficiently detecting small subsurface objects buried in the ground due to surface clutter interference, especially at larger surveillance ranges, where electromagnetic energy penetration is limited and surface backscattering overwhelms subsurface responses.
Innovation Solution
A method utilizing a linear combination of synthetic aperture radar (SAR) images obtained with horizontally and vertically polarized radio waves, employing an adaptive 'minimum energy' polarimetric difference algorithm to cancel out surface clutter while preserving subsurface signals, allowing for improved detection of underground targets using low-frequency SAR systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If radar operates at larger surveillance ranges to detect subsurface objects, then coverage area is improved, but resolution deteriorates due to inability to isolate small volumes of ground
Solution Approach 1:
The patent segments the radar signal into multiple lobes directed at different elevation angles. Each lobe illuminates a specific ground volume, allowing the system to cover large areas while maintaining resolution by processing each segmented view separately and combining them through tomographic reconstruction algorithms.
Solution Approach 2:
The patent introduces elevation angle as an additional dimension for radar observation. By transmitting signals at multiple elevation angles and combining the data, the system achieves 3D tomographic imaging capability, which provides both large coverage and fine resolution by utilizing spatial information from multiple angular perspectives.
2Reliability
If radar transmits electromagnetic energy to detect subsurface objects, then detection capability is improved, but surface clutter interference worsens and overwhelms subsurface responses
Solution Approach 1:
The patent applies different elevation angles to different regions of interest. By directing radar lobes at specific elevation angles tailored to each target area, the system optimizes penetration depth and minimizes surface clutter for each local region, enabling reliable subsurface detection despite varying surface conditions.
Solution Approach 2:
The patent combines radar signals from multiple elevation angles to create a composite image. This composite approach allows the system to separate surface clutter from subsurface targets by exploiting the different angular signatures, effectively filtering out harmful surface backscattering while preserving subsurface target responses.
3Use of energy by moving object
If radar uses conventional single-lob l transmission to improve signal strength, then transmission power efficiency is improved, but surveillance capacity deteriorates due to limited ground area coverage
Solution Approach 1:
The patent merges multiple radar lobes transmitted at different elevation angles into a unified tomographic imaging system. By combining the information from multiple lobes, the system achieves both efficient use of transmitted energy and enhanced surveillance capacity, as each lobe contributes to the overall image reconstruction while covering different ground volumes.
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 surface clutter interference by 6-10 dB, enabling more accurate detection of subsurface targets by enhancing the signal-to-noise ratio and allowing for shorter surveillance ranges, thereby improving detection capabilities without significant loss of target response.
Implementation Method 1
radar is based on electromagnetic radiation
Implementation Method 2
measuring the ground permeability or dielectricity constant
Data Source
Figure 1
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Figure 2b
AI summary
A method and system for obtaining SAR images with reduced or eliminated surface clutter to detect subsurface targets, the method comprising the following steps: - selecting a first frequency and an incidence angle for the radar signal such that the ratio of surface backscattering to subsurface target backscattering is significantly larger for vertical polarization than for horizontal - obtaining vertically and horizontally polarized SAR images based on the same SAR path exploiting the selected first frequency and viewing angle - weighting and differencing the vertically and horizontally polarized SAR images so that the surface backscattering completely cancels between the two images and only the combination of the target backscattering components remains.