Readout Distance Enhancement of the Passive Wireless Multi-Parameter Sensing System Using a Repeater Coil

Lifeng Wang,Lei Dong,Qing-An Huang

doi:10.1155/2018/8950807

Abstract

A repeater coil is used to extend the detection distance of a passive wireless multi-parameter sensing system. The passive wireless sensing system has the ability of simultaneously monitoring three parameters by using backscatter modulation together with channel multiplexing. Two different repeater coils are designed and fabricated for readout distance enhancement of the sensing system: one is a PCB (printed circuit board) repeater coil, and the other is a copper wire repeater coil. Under the conditions of fixed voltage and adjustable voltage, the maximum readout distance of the sensing system with and without a repeater coil is measured. Experimental results show that larger power supply voltage can help further increase the readout distance. The maximum readout distance of the sensing system with a PCB repeater coil has been extended 2.3 times, and the one with a copper wire repeater coil has been extended 3 times. Theoretical analysis and experimental results both indicate that the high Q factor repeater coil can extend the readout distance more. With the copper wire repeater coil as well as a higher power supply voltage, the passive wireless multi-parameter sensing system finally achieves a maximum readout distance of 13.5 cm.

Highlights

Sensor technology is one of the most important technologies in the Internet of things [1]
It is found that the readout distance of the sensing system is the longest when the repeater coil is placed at the midpoint of the reader and the transponder
If the repeater coil is biased toward the reader or the transponder, the final readout distance of the sensing system will be smaller

Summary

Introduction

Sensor technology is one of the most important technologies in the Internet of things [1]. Various passive wireless sensors have been designed and applied to these particular environments, most of which are based on the mechanism of inductive coupling [2–5]. The use of relay coils to increase transmission distance has been studied in wireless power transmission [6, 7]. The detection principle of LC sensor demands the resonant frequency of the repeater coil to be adjustable. As for these problems, a cyclic-scanning repeater is used to enhance the readout distance without frequency splitting and sensitivity reduction. Based on our previous work [11], this paper uses a repeater coil to increase the readout distance of a passive wireless multi-parameter sensing system. A relatively long detection distance, multi-parameter, and passive wireless sensing system is established here

System Design

Experiments and Results

Conclusion