Wireless Information and Power Transfer

4Industrial SWIPT: Backscatter Radio and RFIDs

Panos N. Alevizos* and Aggelos Bletsas

School of ECE, Technical University of Crete, Greece

4.1 Introduction

Radio frequency identification (RFID) is a concrete, industrial example of simultaneous wireless information and power transfer (SWIPT) and dates back to the early 1940s [1]. It is based on backscatter radio, i.e. communications by means of reflection, due to its extraordinary ultra‐low power nature, recently exploited in digital sensor networking [2–5], analog sensor networking [6–8], and IoT [9–11]. Thus, it is interesting to examine such paradigm, under the prism of recent findings in the SWIPT community.

One of the most important problems in state‐of‐the‐art RFID systems is the limited range, due to RF energy harvesting issues at the tag. Far‐field RF energy harvesting circuitry includes one or more diodes for rectification of the incoming RF signal and conversion to DC; such rectification circuits demonstrate highly nonlinear characteristics, as well as limited RF harvesting sensitivity, i.e. output power is zero when the power of the input RF signal is below the sensitivity threshold [12]. Thus, offering an accurate, yet‐tractable model of the tag's harvesting circuit and corresponding output harvested power as a function of input RF power is of vital importance in the SWIPT community. Linear RF harvesting models have been largely incorporated, while nonlinear models have been recently proposed (e.g., [13, 14]). Still, ...