Microwave sensing is important to measure the permittivity of the materials or detecting a material. In this current work, a compact antenna for WLAN application with circular polarization is designed. We are supposed to use it as a sensor to determine the permittivity of industrial oil. For calibration of the sensor, the gasoline and petrol are utilized based on Debye theory and also butanol is checked. This antenna is designed based on Microstrip slot antenna with bent feed line and special split-ring resonator (SRR) as a metamaterial (MTM) element for 4 GHz, it is shown that metamaterial can be considered for improving the Q-factor and matching where the return loss is reduced from −16.5 to −33.5 dB and the Q-factor is increased from 2.39 to 32.9. It covers 4–5 GHz with the bidirectional pattern with gain of 4 dBi which makes it useful for putting inside of liquids. The total dimensions of this resonator are 20 × 20 × 1.6 mm and the FR-4 low-cost substrate is used and the experimental results are confirmed the simulations results by HFSS commercial full-wave software. In fact, this method can be used for fast detecting oil condition and longevity by checking the resonances’ shift and permittivity.

中文翻译：

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基于裂环谐振器的紧凑型天线作为用于液体介电常数测量的高 Q 因数天线

微波传感对于测量材料的介电常数或检测材料很重要。在目前的工作中，设计了一种用于具有圆极化的 WLAN 应用的紧凑型天线。我们应该将其用作传感器来确定工业油的介电常数。为了校准传感器，根据德拜理论使用汽油和汽油，并检查丁醇。该天线基于具有弯曲馈线和特殊裂环谐振器 (SRR) 的微带缝隙天线设计作为 4 GHz 的超材料 (MTM) 元件，表明可以考虑使用超材料来提高 Q 因子和匹配，其中回波损耗从 -16.5 降低到 -33.5 dB，Q 因子从 2.39 增加到 32.9。它覆盖 4–5 GHz 的双向模式，增益为 4 dBi，这使其可用于放入液体内部。该谐振器的总尺寸为 20 × 20 × 1.6 mm，使用 FR-4 低成本基板，实验结果与 HFSS 商用全波软件的模拟结果相一致。事实上，这种方法可以通过检查共振的偏移和介电常数来快速检测油的状况和寿命。