A Battery-Less RFID Sensor Architecture with Distance Ambiguity Resolution for Smart Home IoT Applications

In this paper, a novel battery-less wireless sensor design is proposed and demonstrated. The proposed passive wireless sensor node integrates a UHF 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 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 non-coherent 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.