摘要
A compact antenna formed by three concentric split rings for ultra-high frequency(UHF)radio frequency identification(RFID)tag is proposed in this paper.The antenna is composed of two parts,an outer short-circuited ring modified from a traditional split-ring resonator(SRR)antenna and an inner SRR load,so the antenna can be regarded as a short-circuited ring loaded with SRR.According to the transmission line theory,to conjugate match with the capacitive input-impedance of a tag chip,the length of the short-circuited ring isλg/4 shorter than that of an open-circuited dipole of a traditional SRR antenna,whereλg is the wavelengh of the operating frequency.Hence,the size of the proposed antenna is more compact than that of the traditional SRR antenna.Thereafter,the proposed antenna is simulated and optimized by ANSYS high-frequency structure simulator(HFSS).The impedance,efficiency,and mutual coupling of the fabricated antenna are tested in a reverberation chamber(RC).The results show that the size of the presented antenna is 83%smaller than that of the traditional SRR antenna and the proposed antenna can cover the whole UHF RFID operating frequency band worldwide(840—960 MHz).The measured read range of the tag exhibits maximum values of 45 cm in free space and 37 cm under dense tag environment.
设计了一种由3个同心开口环构成的用于特高频(Ultra⁃highfrequency,UHF)射频识别(Radio frequency identification,RFID)标签的小型化天线。该天线包括1个外部由传统开口环谐振器(Split⁃ringresonator,SRR)天线改进而成的短路环和1个SRR型加载结构,因此该天线可以看作一个内部加载SRR的短路环。根据传输线理论,为了与标签芯片的容性输入阻抗相匹配,采用短路环所需的环长比传统SRR天线的开路环结构短λg/4,由此设计的天线比基于传统SRR结构的天线更加紧凑。其后,采用ANSYS公司的高频结构仿真(High⁃frequency structure simulator,HFSS)软件对所设计的天线进行了仿真与优化。在混响室中测试了所加工的天线的阻抗、效率和互耦。结果表明,本文天线的谐振频段能够覆盖整个特高频射频识别的工作频段(840~960 MHz),且尺寸比传统SRR天线减小83%。在自由空间和密集标签环境中测量所得的标签最大读距分别为45 cm和37 cm。
