Considerations on the Equivalent Electric Models of a UHF RFID Helical Antenna Yarn

The aim of this paper is to present different ways to extract electrical models of an antenna specifically designed for Radio Frequency IDentification (RFID) Ultra High Frequency (UHF) communications. More precisely the models are extracted from a helical dipole designed to operate in the European RFID band and in the context of smart textiles. This kind of antenna was chosen because its electrical properties and radiation pattern are relatively robust with respect to stretching deformation. After presenting the antenna's design, two strategies to extract antenna models are discussed and then compared. The first method is taking into account the antenna's physical dimensions and shape, and the second one, which is a general method relevant to any other antenna geometry, is based on the rational approximation of the antenna's frequency response.

I. Introduction

With the emergence of the Internet of Things (IoT) paradigm, where any object will be connected to data Web services, the market of wireless technologies is going to keep developing [1]. All current “low-power” communication protocols, as for instance Bluetooth Low Energy, Zigbee, Z-Wave, Sigfox or Lora, are potential candidates and also concurrent according to the needs, in terms of notably data rate and communication range.