Non-Line-of-Sight EM Imaging Using Time Reversal and Compressed Sensing
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Solution Overview
Problem
Existing electromagnetic target detection methods struggle to effectively detect targets occluded by metal objects or high-loss media, as they fail to penetrate these obstacles and provide accurate imaging in high scattering environments.
Innovation Solution
The proposed method employs an electromagnetic non-line-of-sight imaging technique based on time reversal and compressed sensing. This involves dividing the target area into grids, using active metasurface radomes to modulate electromagnetic waves, and applying control voltages to achieve time reversal and compressed sensing characteristics, thereby enhancing signal convergence and suppressing multipath clutter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromagnetic waves are used to detect targets in occluded areas, then detection capability in hidden scenes can be improved, but metal objects and high-loss media block the electromagnetic waves and prevent effective detection
Solution Approach 1:
The patent converts the harmful multipath scattering and reflection from metal objects into useful signal components. By applying time reversal processing to the received signals containing multipath components, the method causes scattered waves to converge at the target location, transforming what was previously harmful clutter into beneficial signal enhancement for detecting targets behind occlusions.
Solution Approach 2:
The patent introduces an active metasurface radome as an intermediary between the electromagnetic wave source and the occluded target. This metasurface modulates the electromagnetic waves, enabling them to penetrate or diffract around metal objects and high-loss media, thereby facilitating detection in previously inaccessible occluded areas.
2Measurement precision
If traditional electromagnetic detection methods are used, then simple environments can be detected, but imaging accuracy deteriorates in high scattering environments with occluded targets
Solution Approach 1:
The patent performs preliminary calibration by placing metal objects with known size and shape in each grid to establish detection electromagnetic waves with time reversal characteristics before actual target detection. This pre-established wave pattern enables accurate target imaging in high scattering environments without requiring complex real-time processing during detection.
Solution Approach 2:
The patent changes the phase and amplitude parameters of electromagnetic waves through active metasurface radomes to achieve compressed sensing characteristics. By modulating these parameters across multiple measurements, the system achieves high-resolution imaging in complex scattering environments while reducing the required measurement complexity.
3Reliability
If multiple reflections and obstacle scattering are utilized to improve occluded target detection, then blind area can be reduced, but multipath clutter increases and reduces target recognition ability
Solution Approach 1:
The patent transforms multipath clutter into useful signal components through time reversal processing. The scattered and reflected waves that were previously considered harmful clutter are processed to converge at the target location, enhancing the target signal while suppressing background noise and improving target recognition in occluded areas.
Solution Approach 2:
The patent employs feedback mechanisms where the received signals containing multipath information are processed and fed back into the detection system. Through iterative time reversal and compressed sensing operations, the system continuously refines the target image by utilizing the feedback from multipath components, thereby reducing blind areas while maintaining target recognition accuracy.
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 method effectively improves signal strength and detection accuracy in occluded areas, reduces noise, and expands detection range and application scenarios, enabling precise contour imaging of occluded targets.
Implementation Method 1
placing a metal object with a known size and shape in each grid in sequence when there is no target in the target area, and setting m groups of control voltages to be applied to an antenna to establish m groups of detection electromagnetic waves with time reversal characteristics
Implementation Method 2
electromagnetic waves transmitted by the transmitting antenna array are scattered around the edge of the wall/metal structure and then reach the target
Implementation Method 3
the receiving antenna array receives the scattering electromagnetic wave Emtr of the target
Data Source
AI summary
An electromagnetic non-line-of-sight imaging method based on time reversal and compressed sensing is provided. The electromagnetic signal passively scattered by the target behind the obstacle is received by the antenna, the contour imaging of the target is realized by using compressed sensing, the signal-to-noise ratio of the electromagnetic signal of the target is improved by using time reversal for the contour area, so as to achieve the purpose of staring at and detecting the non-line-of-sight target; a random radiation signal is transmitted for multiple times through active metasurface modulation, compressed sensing is performed for calculation imaging after receiving the signal to judge the number of targets and the contour area in the occluded area; for the target contour area, the amplitude and phase of signals obtained at different positions are adjusted by the active metasurface, so as to focus and scan the electromagnetic signals at different positions behind the obstacle. The method can detect the target in the unsealed scene behind the wall and the metal structure (3) which cannot be penetrated by electromagnetic signals, and expand the detection capability of the traditional detection and imaging radar.