This paper presents a highly sensitive phase-variation sensor for dielectric constant measurements based on a capacitively-loaded periodic slow-wave transmission line. Such line is implemented in microstrip technology, and the loading capacitors are formed by closely spaced rectangular patches. The sensing area of the device is delimited by the region occupied by the capacitive patches, where the material under test (MUT) must be located. The presence of the MUT modifies the coupling capacitance between adjacent patches, thereby producing a variation in the electrical length, or phase of the transmission line, which is the output variable. A detailed analysis of the equivalent circuit model of the unit cell, useful for design purposes, is carried out in the paper. Based on such analysis, a prototype device sensor is designed and fabricated. It is demonstrated in the paper that the sensitivity of the proposed sensor is by far superior to the one achieved in an ordinary meandered line with similar sensing area. Thus, the proposed slow-wave structure constitutes a good alternative to meandered lines for the implementation of phase-variation sensors with simultaneously high sensitivity and compact size.

中文翻译：

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基于电容负载慢波传输线的高灵敏度相变介电常数传感器


本文提出了一种基于电容负载周期性慢波传输线的高灵敏度相位变化传感器，用于介电常数测量。这种线路采用微带技术实现，负载电容器由紧密间隔的矩形贴片形成。器件的传感区域由电容贴片占据的区域界定，被测材料 (MUT) 必须位于该区域。 MUT 的存在会改变相邻贴片之间的耦合电容，从而产生作为输出变量的传输线的电气长度或相位的变化。本文对单元电池的等效电路模型进行了详细分析，这对于设计目的很有用。基于这样的分析，设计并制造了原型设备传感器。论文证明，所提出的传感器的灵敏度远远优于具有相似传感面积的普通曲折线所实现的灵敏度。因此，所提出的慢波结构构成了曲折线的良好替代方案，用于实现同时具有高灵敏度和紧凑尺寸的相位变化传感器。