When vehicles passing ring coil detector, the interaction of vehicle body's substance and ring coil changes resonant frequency of the ring coil and forms a curve of frequency variation.
车辆通过环形线圈检测器时，车体物质与环形线圈相互作用改变了线圈的谐振频率，从而形成频率变化曲线。
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Through the curve of resonant wavelength versus period, we present a new method to analyze the shift of resonant wavelength of LPFG during UV laser writing without solving the coupled-mode equations.