Radar RF Absorber Surface Shaping for Internal Scattering Control
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Solution Overview
Problem
Radar sensors are susceptible to internal scattering of radar waves, which can lead to false detections and ghosting due to the radome contributing to scattering and guiding waves without interacting with RF absorbers, posing safety risks in critical systems like vehicles and complicating calibration.
Innovation Solution
A radar sensor design featuring an RF absorber with a top surface comprising scattering structures such as recesses and protrusions to redirect radar waves out of the field of view, increasing interactions with the radome and absorber, thereby reducing scattered energy and backwards radiation, and optimizing the shape and placement of the absorber within the radome.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the radome covers the RF absorber to protect it from the environment, then the RF absorber is protected, but the radome guides scattered radar waves through its material without interacting with the RF absorber, causing weakly attenuated radar waves to exit outside the FOV
Solution Approach 1:
The patent introduces an interface layer or modified interface between the radome and RF absorber to mediate the interaction. This interface ensures that scattered radar waves are properly directed to interact with the RF absorber material, preventing the radome from acting as a waveguide that bypasses the absorber. The interface acts as an intermediary that couples the electromagnetic fields properly between the two components.
Solution Approach 2:
The patent applies different properties to different regions of the radome-absorber interface. By modifying the local characteristics at the interface (such as impedance matching layers or geometric modifications), the system ensures that scattered waves in specific regions are directed to interact with the absorber, while maintaining the overall protective function of the radome cover.
2Object-generated harmful factors
If the RF absorber is geometrically shaped on its surface to minimize reflected energy, then the reflection level is reduced, but scattered radar waves still propagate in backwards direction without sufficient interaction with the absorber
Solution Approach 1:
The patent employs curved or non-planar geometric shapes on the RF absorber surface, such as spherical, hemispherical, or dome-shaped elements. These curved surfaces scatter incoming radar waves in multiple directions rather than reflecting them specularly, increasing the path length and interaction probability with the absorber material while redirecting energy away from the backwards propagation direction.
Solution Approach 2:
The patent introduces three-dimensional geometric features (protrusions, recesses, or curved surfaces) on the otherwise two-dimensional absorber surface. This dimensional enhancement creates additional scattering centers and interaction paths, transforming simple surface reflections into complex multi-path interactions that increase energy absorption while controlling the angular distribution of scattered waves.
3Measurement precision
If radar waves are reflected inside the radome material in a backwards direction, then scattering occurs, but false detections or ghosting may occur and calibration becomes difficult
Solution Approach 1:
The patent converts the potentially harmful backwards-scattered waves into beneficial interactions by designing the RF absorber geometry to specifically target and absorb these scattered waves. The geometric features are positioned and shaped to intercept waves that would otherwise create ghost targets, transforming a calibration problem into an opportunity for enhanced absorption and detection accuracy.
4Loss of energy
If the RF absorber is made larger to increase interaction with scattered waves, then more energy is absorbed, but the device complexity and material usage increase
Solution Approach 1:
The patent uses curved geometric features that achieve enhanced scattering interaction without requiring a larger overall absorber volume. The three-dimensional curved surfaces provide increased effective interaction area and multiple reflection paths within a compact footprint, maintaining absorption performance while reducing device complexity compared to larger planar absorber designs.
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 design reduces unwanted radar wave propagation and energy reflections, improving azimuth and elevation angle accuracy, minimizing ghost target detection, and reducing the amount of RF absorber material needed, while also lowering the radar cross-section of the sensor.
Implementation Method 1
a top surface comprising at least one scattering structure configured to redirect radar waves out of the field of view and to increase radar wave scattering interactions with the radome and the at least one RF absorber
Implementation Method 2
at least one RF absorber provided with a top surface comprising at least one scattering structure configured to redirect radar waves out of the field of view and to increase radar wave scattering interactions with the radome and the at least one RF absorber
Data Source
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AI summary
Provided is a radar sensor comprising at least one antenna 1 having a FOV 2, at least one RF absorber 9, and a radome 3 covering the at least one antenna 1 and the at least one RF absorber 9, wherein the at least one RF absorber 9 is provided with a top surface 10 comprising at least one scattering structure configured to redirect radar waves out of the FOV 2 and to increase radar wave scattering interactions with the radome 3 and the at least one RF absorber 9. As a result, energy of scattered waves and of backwards radiation is reduced. Further, the amount of RF absorber material is reduced and the RCS of the radar sensor is reduced.