Parameters Calibration Circuit Design Of Passive UHF RFID Tag

Radio frequency identification(RFID)technology has the advantages of contactless,low cost,small size and so on,widely used in the field of identification,transportation,logistic.RFID technology is one of the key technologies to realize the internet of things(IOT),with the combination of internet and mobile communication technology,IOT can be realized.In this paper,the change of clock frequency,LDO voltage,duty cycle of demodulator on the tag chip are analyzed,the conclusion of improving the accuracy of the parameters is obtained.Five calibration techniques are analyzed and the advantages and disadvantages are compared.Three types of the parameters circuit including the clock calibration circuit,Low Dropout Regulator(LDO)voltage calibration circuit,duty cycle calibration circuit of demodulator are designed.According to the clock calibration circuit,analyzed two kinds of structure,including the ring oscillator as the core by changing the charge and discharge current and calibration circuit with a relaxation oscillator as the core by changing the resistance,design the military standard protocol compatible clock calibration command,clock calibration range of 1.55~2.82 MHz,the power consumption is 470,the deviation from-19%~+46% to 2%.Analysis two LDO voltage calibration circuit,including LDO circuit with feedback and LDO calibration circuit without feedback,calibration of output voltage by controlling the value of resistance,according to the LDO voltage calibration circuit with feedback,when the output voltage deviates from the standard value-30%~+15%,after calibration,the output voltage is stable in the range of standard value 6.46%.According to the LDO voltage calibration circuit with feedback,when the output voltage deviates from the standard value-12%~+20%,after calibration,the output voltage is stable in the range of standard value.To change the duty cycle of the demodulator,the duty cycle is changed by changing the size of the output capacitor.The calibration range of the duty cycle is 40%~70% and the power consumption is 450.Finally,the test scheme and test results of clock calibration circuit and LDO circuit are given.Test results show that the clock calibration circuit and the LDO calibration circuit can work properly.