This paper proposes a differential sensor based on a pair of open split ring resonators (OSRR) operating in reflection. The output signal is thus the differential reflection coefficient of both resonators, intimately related to their dielectric loading. Thus, for identical loads in both sensing resonators, the individual reflection coefficients are equal, thereby providing an ideally null output signal. By contrast, when unequal dielectric loads truncate the symmetry, the reflection coefficients are different, resulting in a differential output signal related to the level of asymmetry. In order to ease the measurement of the output signal, a rat-race hybrid coupler is used. The OSRR sensing loads are connected to the coupled ports of the hybrid coupler, whereas the input signal is injected to the Δ-port, and the output signal is collected at the isolated port (Σ-port). By this means, the output signal, i.e. the differential reflection coefficient between both sensing loads, is obtained from the transmission coefficient of a simple two-port structure. For experimental validation purposes, the sensor is applied to the measurement of isopropanol content in aqueous solutions, and for that purpose, the sensitive regions are equipped with microfluidic channels.

中文翻译：

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基于开环谐振器 (OSRR) 的微流控反射模式差分传感器

本文提出了一种基于一对在反射中工作的开环谐振器 (OSRR) 的差分传感器。因此，输出信号是两个谐振器的差分反射系数，与它们的介电负载密切相关。因此，对于两个传感谐振器中的相同负载，各个反射系数相等，从而提供理想的零输出信号。相反，当不相等的介电负载截断对称性时，反射系数不同，从而导致与不对称程度相关的差分输出信号。为了简化输出信号的测量，使用了老鼠赛跑混合耦合器。OSRR 传感负载连接到混合耦合器的耦合端口，而输入信号注入到 Δ 端口，并且输出信号在隔离端口（Σ-端口）收集。通过这种方式，输出信号，即两个传感负载之间的差分反射系数，是从一个简单的双端口结构的传输系数中获得的。出于实验验证目的，传感器用于测量水溶液中的异丙醇含量，为此，敏感区域配备了微流体通道。