A Passive Wireless Adaptive Repeater for Enhancing the Readout of LC Passive Wireless Sensors

In this letter, a passive wireless adaptive repeater is proposed to enhance the readout of LC sensors. The frequency spectrum of the repeater can cover that of the sensor so as to realize full-spectrum-enhancing by strong magnetic coupling. The resonant frequency of the passive wireless adaptive repeater is changed via cyclic-scanning by a controlled voltage which is induced by itself through coupling from the readout coil. An LC humidity sensor, as an example, is then monitored with and without the adaptive repeater. We have demonstrated that the readout distance with the passive wireless adaptive repeater can achieve 3.18 times as long as that without a repeater, while keeping their signal intensity and sensitivity the same.