Interactive RFID for Industrial and Healthcare Applications

University dissertation from Stockholm : KTH Royal Institute of Technology

Abstract: This thesis introduces the circuit and system design of interactive Radio-Frequency Identification (RFID) for Internet of Things (IoT) applications. IoT has the vision of connectivity for anything, at anytime and anywhere. One of the most important characteristics of IoT is the automatic and massive interaction of real physical world (things and human) with the virtual Internet world.RFID tags integrated with sensors have been considered as one suitable technology for realizing the interaction. However, while it is important to have RFID tags with sensors as the input interaction, it is also important to have RFID tags with displays as the output interaction.Display interfaces vary based on the information and application scenarios. On one side, remote and centralized display interface is more suitable for scenarios such as monitoring and localization. On the other side, tag level display interface is more suitable for scenarios such as object identification and online to offline propagation.For tag level display, though a substantial number of researches have focused on introducing sensing functionalities to low power Ultra-High Frequency (UHF) RFID tags, few works address UHF RFID tags with display interfaces. Power consumption and integration with display of rigid substrate are two main challenges.With the recent emerging of Electronic Paper Display (EPD) technologies, it becomes possible to overcome the two challenges. EPD resembles ordinary ink on paper by characteristics of substrate flexibility, pattern printability and material bi-stability. Average power consumption of display is significantly reduced due to bi-stability, the ability to hold color for certain periods without power supplies. Among different EPD types, Electrochromic (EC) display shows advantage of low driving voltage compatible to chip supply voltage.Therefore this thesis designs a low power UHF RFID tag integrated in 180 nm CMOS process with inkjet-printed EC polyimide display. For applications where refresh rate is ultra-low (such as electronic label in retailing and warehouse), the wireless display tag is passive and supplied by the energy harvested from UHF RF wave. For applications where refresh rate is not ultra-low (such as object identification label in mass customized manufacturing), the wireless display tag is semi-passive and supplied by soft battery. It works at low average power consumption and with out-of-battery alert.For remote and centralized display, the limitations of uplink (from tags to reader) capacity and massive-tag information feedback in IoT scenarios is the main challenge. Compared to conventional UHF RFID backscattering whose data rate is limited within hundreds of kb/s, Ultra-wideband (UWB) transmission have been verified with the performance of Mb/s data rate with several tens of pJ/pulse energy consumption.Therefore, a circuit prototype of UHF/UWB RFID tag replacing UHF backscattering with UWB transmitter is implemented. It also consists of Analog-to-Digital Converter (ADC) and Electrocardiogram (ECG) electrodes for healthcare applications of real-time remote monitoring of multiple patients ECG signals. The ECG electrodes are fabricated on paper substrate by inkjet printing to improve patient comfort.Key contribution of the thesis includes: 1) the power management scheme and circuit design of passive UHF/UWB RFID display tag. The tag sensitivity (the input RF power) is -10.5 dBm for EC display driving, comparable to the performance of conventional passive UHF RFID tags without display functions, and -18.5 dBm for UWB transmission, comparable to the state-of-the-art performance of passive UHF RFID tag. 2) communication flow and circuit design of UHF/UWB RFID tag with ECG sensing. The optimum system throughout is 400 tags/second with 1.5 KHz ECG sampling rate and 10 Mb/s UWB pulse rate.