Phaseless Passive SAR Imaging With Fewer Measurements
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Solution Overview
Problem
Conventional Phaseless Passive Synthetic Aperture Radar (PPSAR) imaging systems face challenges with high computational demands, memory intensity, and the need for large training data, especially when using Wirtinger Flow (WF) based approaches, which require numerous measurements and on-board storage, making them unsuitable for resource-constrained platforms.
Innovation Solution
A regularized Wirtinger Flow (rWF) approach is employed, combined with Alternating Direction Method of Multipliers (ADMM) and denoisers like Total Variation (TV), Block-matching and 3D filtering (BM3D), and Deep Image Prior (DIP), to facilitate PPSAR image reconstruction with fewer measurements, removing far field and small scene approximations, and using appropriate regularizers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Wirtinger Flow (WF) based approaches are used for PPSAR image reconstruction, then image reconstruction quality is improved, but computational complexity and measurement requirements increase significantly
Solution Approach 1:
The patent segments the complex WF-based reconstruction process into multiple manageable steps: (1) initial image formation using autocorrelation of Fourier transform signals, (2) regularization term computation based on image priors, and (3) iterative refinement using the regularized cost function. This segmentation reduces computational complexity by breaking down the monolithic reconstruction algorithm into modular operations that can be executed efficiently on resource-constrained platforms.
Solution Approach 2:
The patent introduces regularization parameters (λ₁, λ₂) that control the trade-off between data fidelity and image prior constraints. By adjusting these parameters, the system can adapt the reconstruction quality versus computational cost trade-off dynamically. The regularization terms modify the cost function parameters to incorporate prior knowledge about image structure, enabling quality improvement without proportionally increasing computational burden.
2Measurement precision
If standard WF approaches are used, then reconstruction accuracy is improved, but the number of measurements required increases by 75% compared to the proposed method
Solution Approach 1:
The patent implements an iterative feedback mechanism where the reconstructed image is continuously refined by computing regularization terms based on image priors and feeding them back into the cost function. The algorithm alternates between updating the image estimate and recalculating the regularization constraints, creating a feedback loop that converges to an accurate solution with fewer measurements. This feedback-driven approach allows the system to extract more information from limited measurements through iterative optimization.
Solution Approach 2:
The patent performs preliminary actions by incorporating image prior knowledge (regularization terms) into the reconstruction process before full optimization is complete. By pre-defining constraints based on expected image properties (such as total variation or sparsity), the system narrows the solution space early in the reconstruction process, reducing the number of measurements needed to achieve accurate results.
3Reliability
If multiple receivers are used for passive SAR imaging, then imaging capability is improved, but synchronization complexity and hardware requirements increase
Solution Approach 1:
The patent extracts and eliminates the synchronization requirement by using a single receiver instead of multiple receivers. The method takes out the complex synchronization subsystem entirely and replaces it with signal processing techniques that work with single-receiver data. By extracting only the essential imaging function from the multi-receiver architecture and implementing it through clever signal processing (autocorrelation of phaseless measurements), the system achieves comparable imaging capability without synchronization complexity.
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 proposed method reduces computational complexity and measurement requirements, achieving improved image reconstruction with 75% fewer measurements compared to existing methods, while being more robust to trajectory errors and eliminating constraints on transmitter and receiver locations.
Implementation Method 1
Synthetic Aperture Radar (SAR) imaging is an imaging Radio Detection And Ranging (Radar) system that can obtain high-resolution images
Implementation Method 2
A plurality of Passive Synthetic Aperture Radar (PSAR) imaging signals back scattered from the scene of interest are received by a mobile receiver
Implementation Method 3
generates a plurality of Fourier transform PSAR imaging signals by representing the plurality of PSAR imaging signals into frequency domain using a fast-time Fourier transform
Data Source
AI summary
The present invention relates to a method and system for Phaseless Passive Synthetic Aperture Radar (PPSAR) imaging. Existing method for image reconstruction requires large number of measurements for satisfactory PPSAR image reconstruction. However, this leads to provisioning of more on-board storage and/or a high-speed data link between a mobile platform and a ground station. These requirements are undesirable in practice as PPSAR image reconstruction systems are deployed on resource constrained platforms. The present disclosure uses a regularized Wirtinger Flow (rWF) based approach that uses appropriate regularizers to facilitate the PPSAR image reconstruction with fewer measurements. Further the PPSAR image reconstruction is achieved using Alternating Direction Method of Multipliers (ADMM) by employing standard denoisers such as Total Variation (TV), Block-matching and 3D filtering (BM3D) and, Deep Image Prior (DIP). Further the present disclosure considers an actual location of transmitter for PPSAR imaging that yields better image reconstruction.