Modified Auto-Focusing Algorithm for High Squint Diving SAR Imaging Based on the Back-Projection Algorithm with Spectrum Alignment and Truncation
The study focuses on addressing the image defocusing issue caused by motion errors in highly squinted Synthetic Aperture Radar (SAR). The traditional auto-focusing algorithm, Phase Gradient Autofocus (PGA), is not effective in this mode due to difficulties in estimating the phase gradient accurately...
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-06-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/15/12/2976 |
| _version_ | 1797592820899381248 |
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| author | Anqi Gao Bing Sun Mengyuan Yan Chen Xue Jingwen Li |
| author_facet | Anqi Gao Bing Sun Mengyuan Yan Chen Xue Jingwen Li |
| author_sort | Anqi Gao |
| collection | DOAJ |
| description | The study focuses on addressing the image defocusing issue caused by motion errors in highly squinted Synthetic Aperture Radar (SAR). The traditional auto-focusing algorithm, Phase Gradient Autofocus (PGA), is not effective in this mode due to difficulties in estimating the phase gradient accurately from strong point targets. Two main reasons contribute to this problem. Firstly, the direction of the energy-distributed lines in the Point Spread Function (PSF) does not align with the image’s azimuth direction in highly squinted mode. Secondly, the wavenumber spectrum of high squint SAR images obtained using the Back-Projection Algorithm (BPA) varies spatially, causing aliasing in the azimuth spectrum of all targets. In this paper, a new auto-focusing method is proposed for highly squinted SAR imaging. The modifications to the BP imaging grids have been implemented to address the first problem, while a novel wavenumber spectrum shifting and truncation method is proposed to accurately extract the phase gradient and tackle the spatial variation issue. The feasibility of the proposed algorithm is verified through simulations with point targets and processing of real data. The evaluation of the image shows an average improvement of four times in PSLR (Peak-Sidelobe-to-Noise Ratio). |
| first_indexed | 2024-03-11T01:58:32Z |
| format | Article |
| id | doaj.art-0005d906548544b5879c19ac67aa50b7 |
| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-03-11T01:58:32Z |
| publishDate | 2023-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Remote Sensing |
| spelling | doaj.art-0005d906548544b5879c19ac67aa50b72023-11-18T12:24:31ZengMDPI AGRemote Sensing2072-42922023-06-011512297610.3390/rs15122976Modified Auto-Focusing Algorithm for High Squint Diving SAR Imaging Based on the Back-Projection Algorithm with Spectrum Alignment and TruncationAnqi Gao0Bing Sun1Mengyuan Yan2Chen Xue3Jingwen Li4School of Electronics and Information Engineering, Beihang University, Beijing 100191, ChinaSchool of Electronics and Information Engineering, Beihang University, Beijing 100191, ChinaSchool of Electronics and Information Engineering, Beihang University, Beijing 100191, ChinaSchool of Electronics and Information Engineering, Beihang University, Beijing 100191, ChinaSchool of Electronics and Information Engineering, Beihang University, Beijing 100191, ChinaThe study focuses on addressing the image defocusing issue caused by motion errors in highly squinted Synthetic Aperture Radar (SAR). The traditional auto-focusing algorithm, Phase Gradient Autofocus (PGA), is not effective in this mode due to difficulties in estimating the phase gradient accurately from strong point targets. Two main reasons contribute to this problem. Firstly, the direction of the energy-distributed lines in the Point Spread Function (PSF) does not align with the image’s azimuth direction in highly squinted mode. Secondly, the wavenumber spectrum of high squint SAR images obtained using the Back-Projection Algorithm (BPA) varies spatially, causing aliasing in the azimuth spectrum of all targets. In this paper, a new auto-focusing method is proposed for highly squinted SAR imaging. The modifications to the BP imaging grids have been implemented to address the first problem, while a novel wavenumber spectrum shifting and truncation method is proposed to accurately extract the phase gradient and tackle the spatial variation issue. The feasibility of the proposed algorithm is verified through simulations with point targets and processing of real data. The evaluation of the image shows an average improvement of four times in PSLR (Peak-Sidelobe-to-Noise Ratio).https://www.mdpi.com/2072-4292/15/12/2976image defocusingmotion errorsynthetic aperture radar (SAR)phase gradient autofocus (PGA)Back-Projection Algorithm (BPA)spectrum shifting |
| spellingShingle | Anqi Gao Bing Sun Mengyuan Yan Chen Xue Jingwen Li Modified Auto-Focusing Algorithm for High Squint Diving SAR Imaging Based on the Back-Projection Algorithm with Spectrum Alignment and Truncation Remote Sensing image defocusing motion error synthetic aperture radar (SAR) phase gradient autofocus (PGA) Back-Projection Algorithm (BPA) spectrum shifting |
| title | Modified Auto-Focusing Algorithm for High Squint Diving SAR Imaging Based on the Back-Projection Algorithm with Spectrum Alignment and Truncation |
| title_full | Modified Auto-Focusing Algorithm for High Squint Diving SAR Imaging Based on the Back-Projection Algorithm with Spectrum Alignment and Truncation |
| title_fullStr | Modified Auto-Focusing Algorithm for High Squint Diving SAR Imaging Based on the Back-Projection Algorithm with Spectrum Alignment and Truncation |
| title_full_unstemmed | Modified Auto-Focusing Algorithm for High Squint Diving SAR Imaging Based on the Back-Projection Algorithm with Spectrum Alignment and Truncation |
| title_short | Modified Auto-Focusing Algorithm for High Squint Diving SAR Imaging Based on the Back-Projection Algorithm with Spectrum Alignment and Truncation |
| title_sort | modified auto focusing algorithm for high squint diving sar imaging based on the back projection algorithm with spectrum alignment and truncation |
| topic | image defocusing motion error synthetic aperture radar (SAR) phase gradient autofocus (PGA) Back-Projection Algorithm (BPA) spectrum shifting |
| url | https://www.mdpi.com/2072-4292/15/12/2976 |
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