{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,5]],"date-time":"2026-06-05T13:19:10Z","timestamp":1780665550405,"version":"3.54.1"},"reference-count":27,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2020,9,30]],"date-time":"2020-09-30T00:00:00Z","timestamp":1601424000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"National R&amp;D Program through the National Research Foundation (NRF) of Korea funded by the Ministry of Education, Science and Technology","award":["NRF-2019M1A7A1A02085630"],"award-info":[{"award-number":["NRF-2019M1A7A1A02085630"]}]},{"name":"BK21 Plus Project funded by the Ministry of Education, Korea","award":["21A20131600011"],"award-info":[{"award-number":["21A20131600011"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>A broadband compact-sized planar four-port multiple-input\u2013multiple-output (MIMO) antenna with polarization diversity is presented. The proposed dual circularly polarized (CP) MIMO antenna consists of four G-shaped monopole elements, two of which are left-hand CP and the other two are right-hand CP. A vertical line strip in the G-shaped radiating element acts in balancing the vertical and horizontal electric field components to obtain 90\u00b0 phase difference between them for circular polarization. Also, an I-shaped strip is incorporated between the ground planes of the G-shaped antenna elements to obtain equal voltage level in the proposed MIMO configuration. The dual circular polarization mechanism of the proposed MIMO\/diversity antenna is analysed from the vector current distributions. The impedance bandwidth (S11 \u2264 \u201310 dB) of the MIMO antenna is 105.9% (4\u201313 GHz) and the 3 dB axial ratio bandwidth (ARBW) is 67.7% (4.2\u20138.5 GHz), which is suitable for C-band applications. The overall size of the MIMO antenna is 70 \u00d7 68 \u00d7 1.6 mm3, and the minimum isolation between the resonating elements is 18 dB. The envelope correlation coefficient is less than 0.25, and the peak gain within the resonating band is 6.4 dBi.<\/jats:p>","DOI":"10.3390\/s20195610","type":"journal-article","created":{"date-parts":[[2020,10,1]],"date-time":"2020-10-01T09:04:12Z","timestamp":1601543052000},"page":"5610","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":51,"title":["Dual Circularly Polarized Planar Four-Port MIMO Antenna with Wide Axial-Ratio Bandwidth"],"prefix":"10.3390","volume":"20","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-6260-6353","authenticated-orcid":false,"given":"Sachin","family":"Kumar","sequence":"first","affiliation":[{"name":"School of Electronic and Electrical Engineering, Kyungpook National University, Daegu 41566, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2700-3186","authenticated-orcid":false,"given":"Gwan Hui","family":"Lee","sequence":"additional","affiliation":[{"name":"School of Electronic and Electrical Engineering, Kyungpook National University, Daegu 41566, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Dong Hwi","family":"Kim","sequence":"additional","affiliation":[{"name":"School of Electronic and Electrical Engineering, Kyungpook National University, Daegu 41566, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hyun Chul","family":"Choi","sequence":"additional","affiliation":[{"name":"School of Electronic and Electrical Engineering, Kyungpook National University, Daegu 41566, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kang Wook","family":"Kim","sequence":"additional","affiliation":[{"name":"School of Electronic and Electrical Engineering, Kyungpook National University, Daegu 41566, Korea"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2020,9,30]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2880","DOI":"10.1109\/TAP.2007.905938","article-title":"Increasing channel capacity of an ultrawideband MIMO system using vector antennas","volume":"55","author":"Rajagopalan","year":"2007","journal-title":"IEEE Trans. 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