A Low Complexity Design Framework for NFC-RFID Inductive Coupled Antennas

Abstract

Inductive Wireless Power and Data Transfer (WPDT) technology has become a vital enabler to the globalisation of Internet of Things. Driven by an increasing demand for data within applications and by the need to reduce the devices footprint by transmitting data and power with the same antenna, power transfer efficiency has become a barrier to WPDT systems' performance. To overcome the limitations of power transfer efficiency, current research focuses on the design of efficient integrated circuits and does not consider the challenges of inductive antennas' design and system integration. Hence, current system integration methods used in industry to design receivers for WPDT applications still require expensive experimental benchmarking of antennas. This paper introduces a new framework for inductive WPDT systems integration that focuses on the design of inductive coils and tuning capacitances. First, this framework proposes a new planar rectangular coil inductance formula that achieves an average error of 11% based on the testing of one hundred of coils, which out performs the current state of the art. Then, based on a detailed electrical model of both transmitter and receiver of WPDT systems, our design framework computes the coils geometric parameters and tuning capacitances that will optimize the overall efficiency of the WPDT system. Unlike state of the art design approaches, the main advantage of this framework is that it does not require expensive benchmarking of inductive antennas to find the optimal antenna. Verification of our design framework was achieved through a comparative analysis for Very High Bit Rate 13.56 MHz RFID applications. Results indicate an improvement of more than 15% in overall system power transfer efficiency compared to current state of the art methods within a comparatively more cost effective framework. A sensitivity analysis provides an insight and practical guide to implications of manufacturing variances in component parameters.