Time Reversal Adaptive Interference Canceler for Clutter Suppression
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Solution Overview
Problem
Current imaging technologies face significant challenges in localizing targets in high-clutter environments due to the complexity of channel Green's functions and the need for accurate environmental conditions, particularly in underwater acoustics and electromagnetic domains, where existing methods like matched field processing are expensive and sensitive to environmental variations.
Innovation Solution
The development of a Time Reversal Adaptive Interference Canceler (TRAIC) followed by time reversal beamforming (TRBF), which reshapes the time-reversed backscatter from clutter to minimize energy returns and focuses on targets, allowing for high-resolution imaging without requiring knowledge of scatterer positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If matched field processing is used to provide the channel Green's function, then imaging accuracy is improved, but computational cost becomes prohibitively expensive and the method becomes highly sensitive to accurate knowledge of environmental conditions
Solution Approach 1:
The patent replaces the expensive matched field processing with a simple time reversal operation that can be implemented with basic signal processing. The time reversal mirror uses the recorded signal's time-reversed version as the excitation signal, avoiding the need for complex numerical integration of the wave equation while achieving comparable or superior imaging results
Solution Approach 2:
The time reversal method is self-adapting to the environmental conditions. By recording the impulse response of the actual propagation channel and using its time-reversed version for focusing, the system automatically compensates for environmental variations without requiring external calibration or accurate environmental models
2Measurement precision
If the number of antennas is increased to resolve more scatterers, then imaging resolution is improved, but the system becomes more complex and costly
Solution Approach 1:
The patent transitions from spatial dimension only to time dimension by exploiting the temporal structure of scattered signals. Time reversal operates in the time domain to separate and focus signals from different scatterers, effectively adding a temporal dimension to the imaging process that allows resolution of scatterers with fewer antennas than traditional spatial methods would require
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 provides high-resolution imaging by nulling clutter, suppressing backscatter, and focusing on targets, achieving better localization and imaging performance even in dense scattering environments with fewer antennas than scatterers, as demonstrated in experimental results.
Implementation Method 1
time reversal (TR) can be used in localizing targets in highly cluttered environments
Implementation Method 2
Focusing results from the time reversibility of the wave equation in a non-absorbing medium
Implementation Method 3
time reversing and retransmitting the time dispersed signal received at an array of sensors
Implementation Method 4
time reversal to focus with super-resolution on a source in a highly dispersive medium
Implementation Method 5
Probing the cluttered environment with the reshaped, time reversed waveform whitens and suppresses the backscatter from the clutter
Data Source
AI summary
A high resolution imaging system is used to detect and locate targets using time reversal in rich scattering environments, where the number of scatterers is significantly larger than the number of antennas. Our imaging system performs two major tasks by time reversal: clutter mitigation and target focusing. Clutter mitigation is accomplished through waveform reshaping to suppress the clutter returns. After the suppressed clutter is subtracted from the returned signal, a second time reversal for target focusing is performed. A final image is then obtained by beamforming.