Abstract:In view of the current passive electronic hard label production process,the traditional hard label resonance frequency detection technology is not enough for the insert magnetic rod to adjust frequency control device.The resonant frequency sensing technology of single coil sensitive hard tag based on capacitance compensation principle is proposed.Modeling and simulation analysis of signal amplitude ratio and phase difference variation characteristics based on this technology found that both phase difference and polarity have inversion characteristics.Based on this, the circuit is designed with MSP430F149 single chip microcomputer as control center, fixed frequency signal source, phase detection and phase polarity discrimination.The phase change is used to provide feedback signal for the control system, and the phase difference reversal characteristic is used to realize high and low speed switching, and the phase polarity reversal characteristic is used to complete the control decision of pressing down.This is a kind of frequency modulation control system of inserted magnetic bar, which does not need frequency sweeping and is not affected by the time-varying characteristics of mutual inductance.The production of 58KHz "medium hammer" hard tags was tested, data analysis showed that when the control system runs at a high speed of 20mm/s and a low speed of 5mm/s, the control error of hard label resonance frequency is within±50Hz and the variance is 0.0006~0.0008, and the operation is stable.