基于无源RFID传感标签的农田土壤环境监测技术研究

Monitoring Technology of Farmland Soil Environment Based on Passive RFID Sensor Tag

针对现有农田环境无线传感器网络在长期性、环保性和追踪性方面的不足,提出了一种基于无源射频识别(Radio frequency identification,RFID)传感标签的农田土壤环境监测技术。该RFID传感器标签基于超高频RFID通信协议,且工作于无源模式下。提出了一种新的数据融合方式,比传统数据融合方式显著降低了系统工作的功耗以及响应时间。测试了电磁波在农田土壤中传输的损耗情况,确定了标签可正常工作的基本条件。针对埋入深度超过30 cm时传感器标签传输精确度不足的情况,提出在同一测量点布置两个传感器标签,通过天线极化方向的不同以获取更高的数据传输精确度。通过实验对所设计的温湿度传感器标签进行了通信性能及温湿度测量性能测试。实验结果表明,基于该无源RFID传感器标签所测试的温湿度与传统方式的测试结果基本一致,温度测试误差不超过1.5%,湿度测试误差不超过1%。与现有农田土壤环境监测方法相比,具有便利性强、成本低、寿命长、传感数据易于跟踪定位等显著优点。

The information of soil environment is one of the most important information parameters in precision agriculture. There are some disadvantages lie in current wireless sensor networks in agriculture,including long-time monitoring, environmental protection and tracking ability. According to these disadvantages,a novel wireless monitoring method was proposed based on radio frequency identification（RFID） sensor tag. The RFID sensor tag was based on ultra-high frequency（UHF） electronic product code（EPC） 2 nd generation communication protocol and worked on a passive mode. A new method of data fusion was also proposed. Compared with the traditional data fusion method,the power consumption and response time of the system were significantly reduced. Because of the complex composition of farmland soil,the loss of electromagnetic wave transmission in farmland soil and the basic conditions for the normal work of the tag were determined. In view of the fact that the transmission accuracy of sensor labels was insufficient when the embedding depth was more than 30 cm,two sensor tags at the same measurement point were proposed,and higher data transmission accuracy was obtained through the polarization direction of antennas. The communication performances and the temperature and humidity performances of the proposed sensor tag were tested in laboratory. The experimental results showed that the proposed sensor tag exhibited good consistence with conventional methods. The maximum error of the temperature test was not more than 1. 5%,and the maximum error of the humidity test was not more than1%. Compared with the existing soil environment monitoring methods, it had the advantages of convenience,low cost,long life and rapid positioning.