{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,10]],"date-time":"2026-01-10T01:02:10Z","timestamp":1768006930095,"version":"3.49.0"},"reference-count":46,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2023,1,12]],"date-time":"2023-01-12T00:00:00Z","timestamp":1673481600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["61971329"],"award-info":[{"award-number":["61971329"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["61701393"],"award-info":[{"award-number":["61701393"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["2020ZDLGY02-08"],"award-info":[{"award-number":["2020ZDLGY02-08"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["HTKJ2022KL504019"],"award-info":[{"award-number":["HTKJ2022KL504019"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Natural Science Basis Research Plan in Shaanxi Province of China","award":["61971329"],"award-info":[{"award-number":["61971329"]}]},{"name":"Natural Science Basis Research Plan in Shaanxi Province of China","award":["61701393"],"award-info":[{"award-number":["61701393"]}]},{"name":"Natural Science Basis Research Plan in Shaanxi Province of China","award":["2020ZDLGY02-08"],"award-info":[{"award-number":["2020ZDLGY02-08"]}]},{"name":"Natural Science Basis Research Plan in Shaanxi Province of China","award":["HTKJ2022KL504019"],"award-info":[{"award-number":["HTKJ2022KL504019"]}]},{"name":"National Key Laboratory of Science and Technology on Space Microwave","award":["61971329"],"award-info":[{"award-number":["61971329"]}]},{"name":"National Key Laboratory of Science and Technology on Space Microwave","award":["61701393"],"award-info":[{"award-number":["61701393"]}]},{"name":"National Key Laboratory of Science and Technology on Space Microwave","award":["2020ZDLGY02-08"],"award-info":[{"award-number":["2020ZDLGY02-08"]}]},{"name":"National Key Laboratory of Science and Technology on Space Microwave","award":["HTKJ2022KL504019"],"award-info":[{"award-number":["HTKJ2022KL504019"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>The conventional polar format algorithm (CPFA) is widely used for synthetic aperture radar (SAR) because of its simple and efficient operations. However, due to its wavefront curvature assumption, the CPFA\u2019s depth-of-focus (DOF) is extremely small, which greatly limits the scene size, especially for high-resolution and highly squinted (HRHS) SAR. To solve this problem, an extended PFA (EPFA) is proposed in this study, re-deriving mapping functions by expanding the range history into slant- and cross-range components according to the forms of real data storage. This allows the full use of storage data, which the CPFA cannot achieve due to the large approximations introduced by the projection of echo data onto the ground. The wavefront curvature error is then analyzed and eliminated using a space-variant phase compensation function. Due to the high accuracy of expansion in the slant range plane and the space-variant correction processing, the EPFA has a larger DOF than the CPFA. The EPFA is also more suitable for undulating terrains since it avoids the projection of real data onto the ground plane performed in the CPFA. Using comparative analyses of simulated data and real-world images, the results suggest that the proposed EPFA achieves better focusing effects than the CPFA and is particularly useful for HRHS SAR.<\/jats:p>","DOI":"10.3390\/rs15020456","type":"journal-article","created":{"date-parts":[[2023,1,12]],"date-time":"2023-01-12T04:29:38Z","timestamp":1673497778000},"page":"456","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["Extended Polar Format Algorithm (EPFA) for High-Resolution Highly Squinted SAR"],"prefix":"10.3390","volume":"15","author":[{"given":"Ping","family":"Guo","sequence":"first","affiliation":[{"name":"Xi\u2019an Key Laboratory of Network Convergence Communication, Xi\u2019an University of Science and Technology, Xi\u2019an 710054, China"}]},{"given":"Fuen","family":"Wu","sequence":"additional","affiliation":[{"name":"Xi\u2019an Key Laboratory of Network Convergence Communication, Xi\u2019an University of Science and Technology, Xi\u2019an 710054, China"}]},{"given":"Anyi","family":"Wang","sequence":"additional","affiliation":[{"name":"Xi\u2019an Key Laboratory of Network Convergence Communication, Xi\u2019an University of Science and Technology, Xi\u2019an 710054, China"}]}],"member":"1968","published-online":{"date-parts":[[2023,1,12]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"3595","DOI":"10.1109\/TGRS.2012.2183606","article-title":"Extended nonlinear chirp scaling algorithm for high-resolution highly squint SAR data focusing","volume":"50","author":"An","year":"2012","journal-title":"IEEE Trans. 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