一种利用S参数测量平衡RFID标签天线阻抗的优化方法

针对测量平衡RFID标签天线阻抗的准确性问题，提出了一种利用s参数测量的优化方法。该方法将平衡RFID标签天线等效为双端口网络，通过联合使用端口短路、开路延伸方法测量S参数，根据拐点选取最邻近数据并进行区间的数据拟合，从而计算出天线阻抗。首先 h1 进行了测量理论分析．然后设计了实物测量场景（915MHz频段的RFID天线），并将该优化方法与传统的Bahm方法、无延伸单端口方法、延伸单端口方法进行了对比。结果表明，在工作频段内，该优化方法所测的标签天线的阻抗实部，虚部与仿真结果基本一致，比传统的Balun2及单端口等测摄方法准确；在工作频段外，所测阻抗实部仍然与仿真结果接近，尽管阻抗虚部与仿真结果存在一定的偏差。

An Optimal Method of Impedance Measurement for Balanced RFID Tag Antennas by S-Parameter

In order to improve the accuracy of impedance measurement for balanced RFID tag antennas, an optimal method of using S- parameter is proposed. It[hS] takes the balanced antenna as a two-port network, by jointly using the port-extension with short-circuited configuration and open-circuited configuration methods to measure the S-Parameters[hS], and then calculates the antenna impedance through selecting the closest data based on the measured S-Parameters and executing the interval data fitting. After analyzing the theory of measurement, the optimal method compares with the traditional methods such as Balun method, single-port without extension method and single-port with extension method to measure the impedance of a balanced RFID tag antenna whose frequency is in 915MHz band, respectively[h7]. The results show that,within the operating frequency band,[h8] the measured real parts and imaginary parts are alrqost identical to the simulation results, [hg]the accuracy of this method is better than the other methods~ and outside the operating frequency band, the measured real parts are also close to the simation, though there are some errors with the imaginary parts.