{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T02:40:20Z","timestamp":1760150420222,"version":"build-2065373602"},"reference-count":34,"publisher":"MDPI AG","issue":"22","license":[{"start":{"date-parts":[[2023,11,16]],"date-time":"2023-11-16T00:00:00Z","timestamp":1700092800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This paper mainly investigates the problem of direction of arrival (DOA) estimation for a monostatic MIMO radar. Specifically, the proposed array, which is called a nested\u2013nested sparse array (NNSA), is structurally composed of two nested subarrays, a NA with N1+N2 elements and a sparse NA, respectively, with N3+N4 elements. The design process of NNSA is optimized into two steps and presented in detail. Setting NNSA as transmitter\/receiver arrays, we derive the closed-form expression of consecutive DOFs and calculate the mutual coupling coefficient. Eventually, extensive simulations are carried out and the results verify the superiority of the proposed array over the previous arrays in terms of consecutive DOFs, array aperture and mutual coupling effect.<\/jats:p>","DOI":"10.3390\/s23229230","type":"journal-article","created":{"date-parts":[[2023,11,17]],"date-time":"2023-11-17T00:49:47Z","timestamp":1700182187000},"page":"9230","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["A Nested\u2013Nested Sparse Array Specially for Monostatic Colocated MIMO Radar with Increased Degree of Freedom"],"prefix":"10.3390","volume":"23","author":[{"given":"Ye","family":"Chen","sequence":"first","affiliation":[{"name":"College of Electronic Information Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210000, China"}]},{"given":"Meng","family":"Yang","sequence":"additional","affiliation":[{"name":"College of Electronic Information Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210000, China"},{"name":"CSSC Intelligent Innovation Research Institute, Beijing 100044, China"}]},{"given":"Jianfeng","family":"Li","sequence":"additional","affiliation":[{"name":"College of Electronic Information Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210000, China"}]},{"given":"Xiaofei","family":"Zhang","sequence":"additional","affiliation":[{"name":"College of Electronic Information Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210000, China"}]}],"member":"1968","published-online":{"date-parts":[[2023,11,16]]},"reference":[{"key":"ref_1","unstructured":"Fishler, E., Haimovich, A., Blum, R., Chizhik, D., Cimini, L., and Valenzuela, R. 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