A Batteryless RFID Sensor Architecture With Distance Ambiguity Resolution for Smart Home IoT Applications

In this article, a novel batteryless wireless sensor design is proposed and demonstrated. The proposed passive wireless sensor node integrates a ultrahigh-frequency (UHF) radio-frequency identification (RFID) chip, a filter, and a reactive sensor to enable the reading of environmental conditions wirelessly, without increasing the complexity of a typical RFID chip and substantial loss of the read range. The sensor changes the phase of the reflected RFID signal based on the sensed parameter; whereas, the filter helps in resolving any phase ambiguity that may arise due to the placement of the node at different distances. The phase change is detected at the reader using a noncoherent IQ demodulator. The design can easily integrate any type of sensors, such as temperature, humidity, and water-level sensor. A flood sensor and a temperature sensor were used to demonstrate the performance of the proposed design in a home and office environment.

I. Introduction

Wireless sensors are proliferating with the growth of the Internet of Things (IoT) market. The overall expected value of this market is expected to reach around 11.1 trillion by 2025 [1], [2]. This growth will introduce different types of wireless sensors ranging from monitoring humidity in a room to measuring temperatures in a variety of industries [3]–[9]. As a result, a massive deployment of wireless sensors, around 75 billion devices, is expected by 2025 [1], [10]. In this regard, ultrahigh-frequency (UHF) radio-frequency identification (RFID) technology is the right technology to provide the needed wireless sensors and should be further explored to provide sophisticated designs that not only offer improvement in terms of performance and implementation but also cost of the sensor [5], [11]–[12].