A UHF RFID tag impedance adaptive circuit and its implementation method

Abstract

The invention discloses an ultra-high frequency RFID tag impedance self-adaptive circuit and method. The circuit includes: an antenna; a capacitor array, including n parallel capacitor branches, which are selectively connected under the control of a control signal output by a digital cycle control circuit. pass through a capacitor branch; the digital cycle control circuit outputs n control signals under the control of the input enable signal, and locks in the value when a certain value is scanned to cause the label chip to start working; the AC-DC converter will The wireless signal received by the antenna is converted into a DC voltage; the power-on reset circuit generates a reset signal when the DC voltage is higher than a rated voltage; the reference voltage source circuit generates the reference voltage required to control the operation of the digital cycle control circuit; the voltage divider circuit, The DC voltage is sampled to obtain a divided voltage; the comparator compares the divided voltage with a reference voltage to obtain a comparison output; the logic circuit performs logic operation on the comparison output and the reset signal to obtain the input enabling signal.

Description

technical field [0001] The present invention relates to radio frequency identification (Radio Frequency Identification, RFID) technology, in particular to a UHF RFID tag impedance self-adaptive circuit and its implementation method. Background technique [0002] For a UHF RFID tag, the impedance matching degree between the tag antenna and the tag chip will directly affect the reading and writing distance of the tag. However, during the actual use of the tag, changes in the external environment, process package parasitics, ambient temperature, etc. will affect the impedance matching between the tag antenna and the chip to varying degrees. When the performance of the tag is degraded due to the deterioration of the matching, it is hoped that the matching can be corrected through the automatic adjustment of the chip, so the automatic impedance matching technology of the tag comes into being. [0003] At present, the existing more mature UHF RFID adaptive impedance matching tech...

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Problems solved by technology

[0003] At present, the existing more mature UHF RFID adaptive impedance matching technology is based on the automatic search and comparison scheme, that is, the best matching point is searched or the number of times is used as the stop mark. The disadvantage of this scheme is that no matter whether the tag can be normal or not All work must find the best matching point. This solution greatly affects the inventory speed of the RFID system. Therefore, it is necessary to propose a technical means to alleviate the above problems

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