What does UHF RFID passive tag chip rely on to power?
The research work of RFID Air Interface Based on CDMA in foreign countries is still in the stage of active tag, only send but not receive. The direct reason is usually attributed to the failure of passive tag to realize low power design of chip, which shows that low power design of chip is very necessary. Therefore, only by clarifying the power supply mechanism of passive tags, and then analyzing the application environment of UHF RFID Air interface, can a complete solution be found. This paper aims to introduce the special power supply mechanism of UHF RFID passive tag chip.
UHF RFID passive tag uses wireless power transmission to establish power supply for tag. Therefore, the power supply efficiency is very low and the power supply capacity is very weak. The tag chip must adopt low power design. The chip circuit is powered by charging and discharging the energy storage capacitor on chip. Therefore, in order to ensure the continuous operation of the tag, it is necessary to charge the energy storage capacitor continuously. The RF energy received by the tag has three different applications: voltage doubling rectifier power supply, command signal receiving and demodulation, and response signal modulation and transmission. Among them, the receiving sensitivity of voltage doubled rectifier is restricted by the voltage drop of rectifier diode tube, which becomes the bottleneck of air interface. Therefore, signal receiving and demodulation and response signal modulation and transmission are the basic functions of RFID system. The stronger the power supply capacity of voltage doubled rectifier tag is, the more competitive the product is. Therefore, the criterion of reasonable distribution of received RF energy in the design of tag system is to increase the RF energy supply as much as possible under the premise of receiving signal demodulation and response signal transmission.