{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,31]],"date-time":"2026-03-31T03:15:31Z","timestamp":1774926931349,"version":"3.50.1"},"reference-count":25,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2022,4,16]],"date-time":"2022-04-16T00:00:00Z","timestamp":1650067200000},"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>In this paper, single-element and MIMO microstrip antenna with two pairs of unequal slits is proposed as a circularly polarized antenna with negligible back radiation for 5G mid-band handsets. The unequal pairs of slits are engraved on the antenna patch to guarantee the presence of the circular polarization (CP). The proximity-coupled feeding technique is used to excite the proposed microstrip antenna in order to provide larger antenna \u221210 dB bandwidth which approaches 10.8% (3.48\u20133.87 GHz). A novel analysis technique is proposed in this paper that demonstrates the 3D axial ratio pattern in order to generate CP in the broadside direction without affecting the structure of the ground plane which ensures weak back radiation. The 3 dB axial ratio bandwidth (ARBW) is found to be equal to 4.1% extended along the range (3.58\u20133.73 GHz). To make the design more compatible with the 5G mid-band handsets, the 2 \u00d7 2 MIMO structure of the proposed antenna with reduced mutual coupling (less than \u221220 dB) is also presented in this work. The simulation and measured results are in good agreement, and both verify the CP characteristics and the weak back radiation of the proposed antenna.<\/jats:p>","DOI":"10.3390\/s22083067","type":"journal-article","created":{"date-parts":[[2022,4,19]],"date-time":"2022-04-19T02:39:31Z","timestamp":1650335971000},"page":"3067","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":21,"title":["Single-Element and MIMO Circularly Polarized Microstrip Antennas with Negligible Back Radiation for 5G Mid-Band Handsets"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2523-7165","authenticated-orcid":false,"given":"Falih M.","family":"Alnahwi","sequence":"first","affiliation":[{"name":"Department of Electrical Engineering, College of Engineering, University of Basrah, Basrah 61001, Iraq"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7859-3550","authenticated-orcid":false,"given":"Yasir I. A.","family":"Al-Yasir","sequence":"additional","affiliation":[{"name":"Faculty of Engineering and Informatics, University of Bradford, Bradford BD7 1DP, UK"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8439-7321","authenticated-orcid":false,"given":"Chan Hwang","family":"See","sequence":"additional","affiliation":[{"name":"School of Engineering and the Built Environment, Edinburgh Napier University, Edinburgh EH10 5DT, UK"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2972-9965","authenticated-orcid":false,"given":"Raed A.","family":"Abd-Alhameed","sequence":"additional","affiliation":[{"name":"Faculty of Engineering and Informatics, University of Bradford, Bradford BD7 1DP, UK"}]}],"member":"1968","published-online":{"date-parts":[[2022,4,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Wong, K. (2002). Compact and Broadband Microstrip Antennas, Wiley.","DOI":"10.1002\/0471221112"},{"key":"ref_2","unstructured":"Balanis, C. (2016). 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