Unveiling the Potential: lc passive Wireless Sensors in Modern Sensing Technology
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Unveiling the Potential: LC Passive Wireless Sensors in Modern Sensing Technology The inductor within the sensor plays a critical role in the realm of inductive capacitor (LC) passive wireless sensing technology by facilitating the reception of power from an external readout coil via an inductive coupling mechanism. This inherent feature enables the sensor to operate without the need for direct electrical connections, enabling wireless detection and remote analysis of any changes or perturbations that occur within the sensor's environment [1] One notable advantage of LC passive wireless sensors is their small physical footprint, which makes them ideal for deployment in confined and difficult environments. Because of the logistical complexities associated with physical access, these environments frequently present challenges to conventional wired sensors. As a result, LC passive wireless sensors emerge as a valuable and versatile technological solution, capable of non-invasive, remote, and wireless monitoring and analysis, even in situations where direct access is difficult or impossible [1]. We find a mature state-of-the-art landscape in the realm of sensor applications, which includes domains such as pressure, strain, temperature, humidity, biochemical, and gas sensing. However, as the Internet of Things (IoT) grows, new challenges emerge. Geometric constraints in IoT scenarios frequently necessitate small, non-invasive coils, which reduce magnetic coupling and thus limit the sensor's interrogation distance. Furthermore, the demand for multi-parameter sensing is increasing. Recent efforts have focused on extending the interrogation range in constrained coil setups and enabling sensors to measure multiple parameters at the same time. These advancements address the changing requirements of IoT applications in a rapidly changing environment. Collins pioneered the concept of inductor-capacitor (LC) passive wireless sensors in 1967 [2]. A pair of flat spiral coils were used to create miniature pressure sensors for implantation in the eye. However, it wasn't until the 1990s [3], when micro-electro-mechanical-system (MEMS) technology advanced, that these sensors gained traction. LC sensors offer remote query capability, allowing data retrieval without physical connections or strict alignment requirements [4]. This versatility makes them ideal for challenging scenarios like sensors on moving parts, medical implants, and harsh environments. Another advantage is their "battery-free" operation, resulting in small size and extended lifespan, particularly suited for sealed environments and biomedical implants [5]. LC sensors' simple design also keeps costs low [6], [7]. With the rise of IoT, especially in implantable sensors and wearables, LC passive wireless sensors have gained significant attention and become a vibrant research area [8]–[10]. Operation Principle: A resonant LC circuit is typically formed by a spiral inductor connected to a sensing capacitor. The properties of the capacitor change in response to the specific parameter under observation, resulting in a shift in its resonant frequency. A readout coil is magnetically linked to the LC sensor for wireless communication, and the sensor's resonant frequency is detected by monitoring the impedance or input return loss of the readout coil. Figure 1(a) shows a diagram of the standard configuration of the LC sensor, while Figure 1(b) shows the corresponding equivalent circuit. (a) (b) Download 345.62 Kb. Share with your friends:
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