An Estimation of Resonant Frequency of a Curving RFID Tag
Radio frequency identification (RFID) technology may be applied to cylindrical objects, but the curving of an RFID tag brings on an increase in resonant frequency of the tag antenna. The tag can not function in an excessively curving case, since the deviation of the antenna resonant frequency from working frequency makes a reduction in inductive energy supplied by a transmitter. The variation in antenna resonant frequency is dependant upon column radius of the cylinder and curving angle of the tag. Analytically, it is found that a reduction in central distance, which is determined by column radius and curving angle, between compound straight tracks leads to the decreasing of overall antenna-coil inductance after the curving of the tag. By introducing a curving turn exponent, the overall antenna-coil inductance is calculated. After neglecting the less variation in overall tag capacitance, the antenna resonant frequency may be estimated. The result provides an instruction for designing a curving tag antenna to fit the tag antenna resonant frequency for working frequency of an RFID system.
L. Xu and H. M. Huang, "An Estimation of Resonant Frequency of a Curving RFID Tag", Advanced Materials Research, Vols. 314-316, pp. 1325-1329, 2011