Simple methods using a microstrip coupled-line directional coupler (CLDC) are presented for dielectric constant measurements. The material under test (MUT) is placed on the coupled-line section of the coupler, and either the coupler’s coupling ( $\lvert S_{31} \lvert $ ) or its isolation level ( $\lvert S_{41} \lvert $ ) is considered as the sensor’s response. Putting different MUTs on the microstrip line leads to a change in the effective dielectric constant of the structure and consequently causing a change in the coupling coefficient. In addition, since the isolation level of a microstrip coupled-line coupler depends on the phase velocity difference between the substrate and the medium above the signal strips, putting different MUTs on the line significantly changes the isolation level. This change is significantly greater than the change in $\lvert S_{21} \lvert $ level of a microstrip line when loaded with different MUTs. Validation of the method is presented through measurements for both solid and liquid MUTs.

中文翻译：

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使用高指向性微带耦合线定向耦合器进行简单且高灵敏度的介电常数测量

介绍了使用微带耦合线定向耦合器 (CLDC) 进行介电常数测量的简单方法。被测材料 (MUT) 放置在耦合器的耦合线部分，并且耦合器的耦合 ( $\lvert S_{31} \lvert $) 或其隔离级别 ( $\lvert S_{41} \lvert $) 被认为是传感器的响应。在微带线上放置不同的 MUT 会导致结构的有效介电常数发生变化，从而导致耦合系数发生变化。此外，由于微带耦合线耦合器的隔离等级取决于基板与信号带上方介质之间的相位速度差，因此在线路上放置不同的MUT会显着改变隔离等级。这种变化明显大于变化 $\lvert S_{21} \lvert $加载不同 MUT 时微带线的电平。通过对固体和液体 MUT 的测量来验证该方法。