3/4 Spatially Variant Apodization for SAR Imaging
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Solution Overview
Problem
Current spatially variant apodization (SVA) solutions for image processing in synthetic aperture radar (SAR) systems are wasteful of pixel real-estate and memory due to high oversampling, and they fail to manage wrap-around and edge effects effectively, leading to inefficient processing and memory usage.
Innovation Solution
A new 3/4 spatially variant apodization (SVA) algorithm that uses a 3/4 filled aperture prior to two-dimensional discrete Fourier transform (DFT) processing, employing two levels of phase testing with convolution kernels at different spacings to suppress sidelobes without sacrificing resolution, resulting in coarser pixel spacing and reduced oversampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional spatially variant apodization (SVA) solutions are used with high oversampling, then sidelobe suppression is achieved, but pixel real-estate and memory usage increase significantly
Solution Approach 1:
The patent changes the aperture filling ratio parameter from traditional high oversampling values (1/2, 1/3, or higher integer ratios) to a specific 3/4 filling ratio. This parameter change reduces the amount of zero-filling required while maintaining effective sidelobe suppression, thereby reducing memory usage and processing requirements without sacrificing image quality.
Solution Approach 2:
The patent applies partial action by using a 3/4 filled aperture instead of fully oversampling the entire aperture. This partial filling approach provides sufficient sidelobe suppression for practical applications while avoiding the excessive memory consumption and processing overhead associated with traditional high oversampling methods.
2Object-affected harmful factors
If high oversampling is used in SVA processing, then sidelobe suppression is improved, but computational overhead and processing time increase
Solution Approach 1:
By changing the aperture filling ratio to 3/4, the patent reduces the size of the data matrix that requires processing. This parameter change decreases the computational load for Fourier transforms and subsequent processing operations, thereby reducing processing time and computational overhead while maintaining effective sidelobe suppression.
3Object-affected harmful factors
If traditional SVA algorithms are used, then sidelobe reduction is achieved, but wrap-around and edge effects are not managed effectively
Solution Approach 1:
The patent applies local quality by implementing spatially variant apodization that adapts to different regions of the aperture. The 3/4 filled aperture configuration with optimized convolution kernels provides differentiated handling for edge and central regions, effectively managing wrap-around and edge effects while maintaining sidelobe suppression throughout the image.
Data Source
AI summary
A new spatially variant apodization (SVA) algorithm that uses a 3/4 filled aperture prior to two dimensional discrete Fourier transform (2-D DFT) to form the image. The algorithm can be used, for example, to improve contrast and resolution on synthetic aperture radar (SAR) imagery, with a lower degree of oversampling (and thus, fewer pixels) than other algorithms require. This can translate into more efficient use of radar displays and processor memory. Additional efficiencies of memory and computing power may be realized when Automatic Target Recognition (ATR) algorithms operate on this imagery. Embodiments of this invention use convolution kernels at two different spacings, which are better tuned to the local phase relationships of mainlobe and sidelobes with a 3/4 filled aperture. As such, these embodiments suppress sidelobes without sacrificing resolution, at an aperture-filling ratio of 3/4, rather than 1/2, as is usually used.