A printable trapezoid-structured UWB micro-strip antenna applicable to MEMS wireless sensor networks

Abstract

This paper comprises of two related works. Firstly, a printable trapezoid-structured UWB micro-strip antenna applicable to MEMS wireless sensor networks (WSN) is proposed from the view point of both the return loss and the impedance bandwidth. A dimensionless parameter, defined as the width ratio of the top edge to the bottom edge of the proposed trapezoid-structure, is introduced to explore the relevance between the trapezoidal geometry and the S11 curve. An optimized trapezoidal structure with better S11 curve is achieved and expected to have various WSN applications. Secondly, a wireless electric current sensor via integrating a magnetic piezoelectric cantilever and the optimized trapezoidal-structured micro-strip antenna is presented for the first time to show the applicability to WSN preliminarily. The wireless current sensor system, consisting of both the magnetic piezoelectric cantilever for measuring electric currents and the trapezoidal-structural micro-strip antenna for transmitting output voltages, are designed and integrated for demonstration, at an operating frequency of 3 GHz with the lowest return loss. Although output errors of 2–7% are observed for output voltage range of 88–116 mV, the signal transmission measurement demonstrates that the proposed integration is experimentally feasible and effective. Due to the ultra-wideband (2–11 GHz) and low power consumption of the integrated micro-strip antenna, the proposed integration is expected to be applicable to various kinds of wireless sensor nodes of different frequencies or multi-sensors monitoring systems.