Subsurface Imaging Radar Using Brewster Angle Refraction
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Solution Overview
Problem
Current radar technologies face challenges in achieving sufficient resolution for detecting small subsurface objects buried in the ground, as they struggle with range attenuation and require large antennas for high resolution, which are impractical for airborne platforms, and existing synthetic aperture radar (SAR) methods are not effective for underground imaging due to limited electromagnetic penetration.
Innovation Solution
A subsurface imaging radar device with a transmitting unit that transmits a vertically polarized radio wave signal at a selected elevation angle, utilizing the Brewster angle to refract energy into the ground, and operates as a wavelength resolution limited synthetic aperture radar for three-dimensional imaging, allowing for high azimuth resolution and efficient energy penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional radar is used for subsurface imaging, then electromagnetic radiation can penetrate the ground, but the resolution is insufficient for detecting small subsurface objects
Solution Approach 1:
The patent changes the polarization parameter of the electromagnetic signal from horizontal to vertical polarization. This parameter change enables the radar to exploit Brewster angle refraction, allowing energy to be refracted into the ground at shallow incidence angles. This resolves the contradiction by maintaining sufficient penetration while achieving the high resolution needed for small subsurface object detection.
Solution Approach 2:
The patent transitions from conventional 2D surface imaging to 3D subsurface volumetric imaging by implementing a volumetric rendering pipeline that processes radar echoes through back-projection algorithms. This dimensional extension allows simultaneous visualization of subsurface objects at different depths, resolving the limitation of detecting small objects buried at varying depths.
2Measurement precision
If large antennas are used to achieve high resolution, then azimuth resolution improves, but the antenna becomes impractical for airborne platforms
Solution Approach 1:
The patent replaces the mechanical constraint of large physical antennas with a computational approach using synthetic aperture radar (SAR) techniques. By collecting radar echoes along the flight path and processing them through back-projection algorithms, the system achieves high azimuth resolution equivalent to large antennas without the mechanical burden, making it suitable for airborne platforms.
Solution Approach 2:
The patent adds the time dimension to the spatial dimensions by collecting radar data continuously along the flight path. This temporal extension allows synthesis of a large effective aperture through processing, achieving high azimuth resolution without requiring a large physical antenna structure on the airborne platform.
3Measurement precision
If existing synthetic aperture radar methods are used, then high 2D resolution of ground surface is achieved, but they are not effective for underground imaging due to limited electromagnetic penetration
Solution Approach 1:
The patent fundamentally changes the illumination parameter by using vertically polarized signals at Brewster angle incidence instead of horizontally polarized signals. This parameter change enables effective electromagnetic penetration into the ground by exploiting refraction physics, allowing the SAR system to image subsurface objects while maintaining high 2D resolution capabilities.
Solution Approach 2:
The patent introduces a specialized signal processing intermediary layer that includes a volumetric rendering pipeline and back-projection algorithms. This intermediary processing stage transforms the refracted radar echoes into 3D subsurface images, bridging the gap between surface SAR techniques and underground imaging requirements.
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
The solution enables effective three-dimensional imaging of subsurface objects by refracting energy into the ground, achieving high azimuth resolution and allowing detection of small targets, even those several times smaller than the radar wavelength, with a compact antenna configuration suitable for airborne platforms.
Implementation Method 1
a significant part of the energy in a vertically polarized signal, with reference to the ground, is trapped in a surface wave mode which is successively tapped by refraction into the ground area
Implementation Method 2
refracting energy into the ground
Implementation Method 3
a second signal being the reflected first signal from the selected ground area
Data Source
Figure 1
Figure 2a~2b
Figure 3
AI summary
The present invention can be summarized by use of a diffraction limited SAR giving large integration angle and a short depth of field which gives that energy from underground targets is focused independently at different depths to enable 3d imaging. The radar device according to the invention should be implemented by considering the following parameters: Choice of the appropriate illumination geometry, i.e. elevation angle θ, and the appropriate use of low frequency diffraction limited SAR processing to obtain 3D imaging, and the choice of an appropriately low radar frequency.