超高频射频识别近场系统互耦效应中频率偏移研究

在超高频射频识别(UHF RFID)系统近场(NF)密集标签应用中，由于微带标签天线的结构特点，传统线圈间互阻抗表达式在预估系统频率偏移等互耦效应问题方面误差较大，精确性不够。首先，基于变压器模型，从无线电能传输的角度推导了近场密集标签间的互阻抗表达式。然后，结合近场电感耦合型标签，通过建立电磁仿真模型间接获取有关电气参数值。最后，验证推导公式并从影响双标签间互阻抗的环境因素角度去研究UHF RFID近场频率偏移问题。测试结果表明，当标签间距小于30 mm时，推导的互阻抗表达式应用于频率偏移计算误差范围为1.6～7.3 MHz。研究结果为基于标签间互阻抗预估UHF RFID近场标签间的互耦效应问题提供了参考依据。

Study on Frequency Shift in Mutual Coupling Effect of Ultra-high-frequency Radio Frequency IDentification Near-field System

In Near-Field (NF) applications of Ultra-High-Frequency Radio Frequency IDentification (UHF RFID) systems, due to the structural characteristics of the microstrip tag, the traditional inter-coil mutual impedance expression has a large error in the estimation of the mutual coupling effect such as the frequency shift of the prediction system, and the accuracy is not enough. Firstly, based on the transformer model, the mutual impedance expressions of the NF dense tags are derived from the perspective of radio energy transmission. Then, the electrical parameter values are obtained indirectly by establishing the electromagnetic simulation model combining with the NF inductance coupling tag. Finally, the derivation formula is verified and UHF RFID NF frequency shift is studied from the perspective of environmental factors that affect the mutual impedance between the two tags. The test results show that the derived mutual impedance expression is applied to the frequency offset calculation with error range in 1.6～7.3 MHz when the tags’ spacing is less than 30 mm. The results provide a reference for studying the mutual coupling effect between UHF RFID NF tags based on the mutual impedance between tags.