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Dual‐polarized metasurface‐based monopole antenna design using characteristics mode theory for UHF RFID applications

In this research article, a printed dual‐polarized metasurface (MTS) inspired printed monopole antenna using characteristics modes theory (CMT) is investigated for UHF RFID applications. A T‐shaped monopole with U‐shaped asymmetric stubs is designed to generate circular polarization (CP) radiation traits. The grounded MTS layer is constructed with array of unit cells and fixed at air‐gap of λo/4 with reference to the monopole radiator (λo is free‐space wavelength at CP frequency band, 945 MHz), offering good impedance bandwidth (IBW), stable CP boresight radiation gain, and high radiation efficiency. By using CMT, interpretation of CP characteristics is highlighted, that is, the resonating modes exhibit asymptotic nature at the designated CP band with symptotic nature above and beyond the designated operating bands. Dual‐polarized characteristics are observed in both principal planes, due to the effect of grounded MTS loading. The prototype antenna of 0.315λo × 0.315λo is designed and validated. It operates from 836 to 1066 MHz with 24.18% IBW, 5.23% 3‐dB axial ratio bandwidth (ARBW) from 905.1 to 950 MHz and attains >6.8 dBic as a CP peak gain with the total efficiency of >83%. Prior to the attainment of good CP attributes in UHF RFID bands, it can be used for RF energy harvesting and wireless power transmission.