Through-the-Wall Radar Imaging Clutter Reduction
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Solution Overview
Problem
Through-the-wall radar imaging systems face challenges in reducing artifacts and improving image quality due to indirect secondary reflections from walls, which result in cluttered radar images.
Innovation Solution
A method using a randomized Kaczmarz algorithm that jointly estimates a sparse scene and removes clutter induced by internal wall reflections, allowing for memory-efficient processing, especially in handheld or mobile devices, by transmitting and receiving radar pulses from multiple locations and updating the image based on received echoes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional time-domain representation is used to generate radar images, then the imaging process is straightforward, but the received signal is corrupted with indirect secondary reflections from walls resulting in artifacts and clutter
Solution Approach 1:
The patent segments the received signal into primary reflections and multi-path reflections by modeling the impulse response as a sum of direct path components and wall-induced delayed components. This segmentation allows separate processing of useful signals and harmful clutter, improving image quality while eliminating wall reflection artifacts
Solution Approach 2:
The patent converts the harmful wall reflection artifacts into useful information by modeling the multi-path delay kernel d(t, nr, ns) that characterizes the wall's reflective properties. By estimating this kernel from the received signals, the system transforms clutter into a characterizable phenomenon that can be compensated for, thereby improving through-the-wall imaging accuracy
2Reliability
If arrays of transmitting and receiving antennas are used for TWI, then the system can detect objects behind walls, but the device complexity increases
Solution Approach 1:
The patent implements a transceiver that can function as both transmitting antenna and receiving antenna by switching between transmission and reception modes. This multi-functionality reduces the need for separate transmitting and receiving antenna arrays, simplifying the overall system configuration while maintaining full detection capability for through-the-wall imaging
Solution Approach 2:
The patent combines the transmitting and receiving antenna functions into a single integrated antenna array system. By merging these functions and using signal processing to separate transmitted and received signals, the system reduces hardware complexity and device size while preserving the ability to detect objects behind walls
3Measurement precision
If signal processing is performed to remove clutter, then image quality improves, but the processing time and computational resources increase
Solution Approach 1:
The patent performs preliminary estimation of the multi-path delay kernel d(t, nr, ns) and wall impulse response gw(t, nr, ns) from the received signals before generating the final radar image. By pre-characterizing the wall reflection effects, the system can efficiently remove clutter during image generation without requiring extensive post-processing, thereby reducing overall processing time while maintaining high image quality
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 improves the quality of through-the-wall radar images by reducing clutter and identifying the number, locations, and shapes of objects behind the wall, even without prior knowledge of scene geometry, and can be implemented in devices with integrated antennas and display screens.
Implementation Method 1
a transmitting antenna array emits a radar pulse that propagates through the wall. The pulse is reflected by the objects and propagate back to a receiving antenna array as a set of echoes
Implementation Method 2
The pulse is reflected by the objects and propagate back to a receiving antenna array as a set of echoes
Implementation Method 3
the received signal is often corrupted with indirect secondary reflections due to the walls, which result in artifacts, such as ghosts, that clutter the radar image
Data Source
AI summary
A method and system for generating an image of a scene behind a wall, wherein the scene is represented as a grid, by first transmitting a radar pulse through the wall using a transmitter and receiving a set of echoes corresponding to the radar pulse being reflected by the scene in a receiver at a known location. Based on the location, an imaging operator that relates the set of echoes to the grid is determined. Using the imaging operator, a sparse delay kernel that matches a response of a current image to a similar response in the set of echoes is determined. Then, the current image is updated, based on the set of echoes, the imaging operator, and the sparse delay kernel. The transmitting, the receiving, the determining, the obtaining, and the updating steps are repeated for different locations until a termination condition is reached.