基于ELC谐振器的湿度传感器

摘要

LC谐振式湿度传感器因无源无线,可极大拓展传感器应用范围,已成为湿度传感器的研究热点之一.将超常媒质(metamaterials)应用在谐振器的结构选择上,解决了传统LC谐振式传感器尺寸过大,灵敏度较低的问题.湿度传感器由电耦合LC谐振器(ELC谐振器)和聚乙烯醇(PVA)敏感薄膜构成.首先利用电磁仿真软件,分析ELC谐振器主要结构参数对谐振特性的影响,设计和制作谐振频率为2.45 GHz的谐振器,品质因数达到302.然后通过滴涂法将制备好的感湿材料聚乙烯醇溶液涂敷在ELC谐振器表面制作湿度传感器,并进行了湿度敏感测试.实验结果显示:ELC谐振器在全频段内磁导率均为正,在频段2.19 GHz~2.98 GHz内介电常数为负,具有超常媒质特性;湿度传感器在相对湿度35% RH~88% RH范围内,谐振频率共偏移69.875 M,且在83%~88% RH湿度范围内感湿灵敏度η达到71.5 MHz/% RH.研究表明ELC谐振器因超常媒质特性实现了结构小型化,且由于品质因数较高改善了湿度灵敏度.%LC-resonanted humidity sensor has become a research focus which because it's wireless passive and can extends application greatly.Metamaterials is selected as the resonator structure to deal with problems of large size and low sensitivity that the conventional LC-resonanted humidity sensor exists.The humidity sensor consists of an ELC resonator and polyvinyl alcohol film.Firstly,through analyzing the effect of the ELC resonator's main structural parameters on resonant characteristics by electromagnetic simulation software,an ELC resonator is designed and made.It has a resonant frequency of 2.45 GHz and quality factor of 302.Then,the humidity sensor is fabricated through coating the prepared polyvinyl alcohol solution on the surface of ELC resonator by drop coating method.At last,its humidity sensitivity is tested by utilizing two antennas in microwave mode without any external circuit.The experimental results show that permeability is positive in the whole band and permittivity is negative from 2.19 GHz to 2.98 GHz.The experimental results show that this humidity sensor shifts 69.875 MHz totally when the relative humidity range from 35% RH to 88% RH and humidity sensitivity η reaches 71.5 MHz/% RH at 83% RH~88% RH.Studies show that ELC resonator as the humidity sensor's structure achieves miniaturization and high quality factor which improves the humidity sensitivity due to its metamaterials's property.