近接するRFタグの共振特性の変化を利用した非接触変位センサ

抄録

A radio frequency tag device is comprised of an inductor, a resistor and a capacitor. These devices are widely used as a resonant markers for detecting shoplifting and in other applications. They are small and light and so may be applicable for use in position sensing, vehicle navigation, or product verification. When the excitation frequency of an electromagnetic wave radiating from an antenna traverses resonances, an electrical ring-down may be generated in the detected circuit, so an RF tag device can be easily detected and its resonant frequency can be easily determined. In this paper I have examined the performance of a detection system consisting of RF tag devices and an antenna. In particular, I have measured and calculated resonant frequencies in the cases of two tag devices located with slight horizontal or vertical displacement with respect to each other. Experi-mental and theoretical examinations reveal that changes of the resonant frequency can be described in terms of mutual inductance between the two tag devices and that the surveillance range depends on the mutual inductance between an RF tag device and an antenna. These results prove that an electric system composed of RF tag devices and a detection antenna can be useful for positioning in the fields of flexible manufacturing systems.