Lopato Przemyslaw, Herbko Michal
Department of Electrical and Computer Engineering, West Pomeranian University of Technology, ul. Sikorskigo 37, Szczecin 70-313, Poland.
Sensors (Basel). 2018 Jan 20;18(1):310. doi: 10.3390/s18010310.
In this paper, a circular microstrip antenna for stress evaluation is studied. This kind of microstrip sensor can be utilized in structural health monitoring systems. Reflection coefficient is measured to determine deformation/strain value. The proposed sensor is adhesively connected to the studied sample. Applied strain causes a change in patch geometry and influences current distribution both in patch and ground plane. Changing the current flow in patch influences the value of resonant frequency. In this paper, two different resonant frequencies were analysed because in each case, different current distributions in patch were obtained. The sensor was designed for operating frequency of 2.5 GHz (at fundamental mode), which results in a diameter less than 55 mm. Obtained sensitivity was up to 1 MHz/100 MPa, resolution depends on utilized vector network analyser. Moreover, the directional characteristics for both resonant frequencies were defined, studied using numerical model and verified by measurements. Thus far, microstrip antennas have been used in deformation measurement only if the direction of external force was well known. Obtained directional characteristics of the sensor allow the determination of direction and value of stress by one sensor. This method of measurement can be an alternative to the rosette strain gauge.
本文研究了一种用于应力评估的圆形微带天线。这种微带传感器可用于结构健康监测系统。通过测量反射系数来确定变形/应变值。所提出的传感器通过粘接连接到被研究的样品上。施加的应变会导致贴片几何形状发生变化，并影响贴片和接地平面中的电流分布。贴片电流的变化会影响谐振频率的值。本文分析了两种不同的谐振频率，因为在每种情况下，贴片内都获得了不同的电流分布。该传感器设计用于2.5GHz的工作频率（基模），其直径小于55mm。获得的灵敏度高达1MHz/100MPa，分辨率取决于所使用的矢量网络分析仪。此外，定义了两种谐振频率的方向特性，通过数值模型进行研究并通过测量进行验证。到目前为止，微带天线仅在已知外力方向的情况下用于变形测量。所获得的传感器方向特性允许通过一个传感器确定应力的方向和值。这种测量方法可以替代应变片。
