The performance of the UHF passive tags mainly is decided by two aspects: the size of the tag antenna gain, and impedance matching between the antenna and the NFC CARD. A way to improve the gain is more than parallel folded dipole substructure, because of the extra dipole radiation impedance can improve the efficiency of the antenna, so this article puts forward in traditional dipole antenna structure (see figure 2) on a circular microstrip line, without any increase in antenna area obtain gain increased
The antenna structure by the variant bending dipole radiator and circular and rectangular combo cards line feeding ring of three parts, the chip on the rectangular feed ring opening of incentives, energy using inductively coupled to the two together in the middle of bending dipole radiation on the body. Dipole adopts stepped bending shape can reduce the total length of the antenna, the compact structure
fConnect the ground size is another factor of influence on antenna performance. Through simulation study found that the size of the metal surface change on the resonant frequency and input impedance,contactless cards is affected, but the radiation efficiency, the influence of the pattern is bigger
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