用于土壤温湿度检测的声表面波标签天线设计

Design of Surface Acoustic Wave Tag Antenna for Soil Temperature and Moisture Measurement

摘要:

天线设计是实现基于无线无源声表面波标签的土壤温湿度检测的重要环节。为实现对同一表面位置不同深度处土壤温湿度的并行检测，多个标签需采用时分与频分多址的方案。对此设计了层叠式双频圆极化微带天线及一分四 T 型微带功分器，天线的不同贴片对应不同谐振频率，通过切角实现圆极化；功分器采用微带线设计减小了高频段电阻效应及耗散功率问题。使用 HFSS 软件进行仿真优化，制作实物并结合矢量网络分析仪进行测试。测试结果表明，该天线在中心频率 842. 5 MHz 与 922. 5 MHz 处的 S₁₁均小于?10 dB，功分器 4 个输出端口的传输系数均约为?6. 8 dB，与仿真结果基本一致，验证了该天线及功分器的实用性。

Abstract:

Antenna design is a critical component in soil temperature and moisture measurement systems utilizing wireless passive surface acoustic wave tags. To enable simultaneous and parallel detection at various depths in the same surface location， a time-division and frequency-division multiple access strategy must be implemented across multiple tags. This paper presents the design of a laminated dual-frequency circularly polarized microstrip antenna alongside a quarter-wave four-way microstrip power divider. The antenna’s distinct patches correspond to specific frequencies and achieve circular polarization through angular truncation. The power divider employs microstrip lines to mitigate issues caused by high-frequency resistance and power dissipation. Simulations and optimizations were conducted using HFSS software， followed by actual fabrication and testing. The results from the vector network analyzer indicate that the antenna’s S₁₁ parameter remains below ?10 dB at the central frequencies of 842. 5 MHz and 922. 5 MHz， with the transmission coefficients of the power divider’s four output ports approximately ?6. 8 dB. This validates the simulation results and confirms the practicality of both the antenna and the power divider.