A Cyclic Scanning Repeater for Enhancing the Remote Distance of LC Passive Wireless Sensors

Inductor-capacitor (LC) passive wireless sensors have been used in situations where wired connections are impossible. When this scheme is applied to implanted or sealed fields, the sensors are required to be scaled down to small dimensions, which results in the limited remote distance. Here we present an approach to enhance the remote readout distance of the LC sensors by a cyclic-scanning repeater. The resonant frequency of the repeater is cyclic-scanned so as to detect that of the LC sensor, and the readout distance is enhanced by strong magnetic coupling. The proposed full-spectrum-enhancing approach has the simplified circuits when compared with other readout enhancement ways. An LC humidity sensor, as an example, is then monitored both with and without the proposed repeater. We have demonstrated that the readout distance with the cyclic-scanning repeater can achieve 3 times long as that without a repeater, while keeping the same for their signal intensity and sensitivity. Overall, this approach with the cyclic-scanning repeater enables a longer detection range and broader applications in the implanted or sealed fields.