{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T04:31:12Z","timestamp":1760243472417,"version":"build-2065373602"},"reference-count":48,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2013,3,14]],"date-time":"2013-03-14T00:00:00Z","timestamp":1363219200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Remote Sensing"],"abstract":"<jats:p>High-altitude platforms (HAP) or near-space vehicle offers several advantages over current low earth orbit (LEO) satellite and airplane, because HAP is not constrained by orbital mechanics and fuel consumption. These advantages provide potential for some specific remote sensing applications that require persistent monitoring or fast-revisiting frequency. This paper investigates the azimuth-variant signal processing in HAP-borne bistatic synthetic aperture radar (BiSAR) with spaceborne or airborne transmitter for high-resolution remote sensing. The system configuration, azimuth-variant Doppler characteristics and two-dimensional echo spectrum are analyzed. Conceptual system simulation results are also provided. Since the azimuth-variant BiSAR geometry brings a challenge for developing high precision data processing algorithms, we propose an image formation algorithm using equivalent velocity and nonlinear chirp scaling (NCS) to address the azimuth-variant signal processing problem. The proposed algorithm is verified by numerical simulation results.<\/jats:p>","DOI":"10.3390\/rs5031292","type":"journal-article","created":{"date-parts":[[2013,3,14]],"date-time":"2013-03-14T12:22:04Z","timestamp":1363263724000},"page":"1292-1310","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Azimuth-Variant Signal Processing in High-Altitude Platform Passive SAR with Spaceborne\/Airborne Transmitter"],"prefix":"10.3390","volume":"5","author":[{"given":"Wen-Qin","family":"Wang","sequence":"first","affiliation":[{"name":"School of Communication & Information Engineering, University of Electronic Science andTechnology of China, Chengdu 611731, China"}]},{"given":"Huaizong","family":"Shao","sequence":"additional","affiliation":[{"name":"School of Communication & Information Engineering, University of Electronic Science andTechnology of China, Chengdu 611731, China"}]}],"member":"1968","published-online":{"date-parts":[[2013,3,14]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"305","DOI":"10.3390\/rs3020305","article-title":"Spaceborne differential SAR interferometry: Data analysis tools for deformation measurement","volume":"3","author":"Crosetto","year":"2011","journal-title":"Remote Sens"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"621","DOI":"10.3390\/rs3030621","article-title":"Airborne remote sensing of a biological hot spot in the southeastern Bering sea","volume":"3","author":"Churnside","year":"2011","journal-title":"Remote Sens"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1939","DOI":"10.1109\/JPROC.2011.2159690","article-title":"The role of high-altitude platforms (HAPs) in the global wireless connectivity","volume":"99","author":"Mohammed","year":"2011","journal-title":"Proc. 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