Tag Antenna-Based Sensing (TABS)

RFID tags are used to wirelessly obtain ID information from objects in the environment. RFID readers typically analyze a tag's response signal and extract the ID information. Most business processes just focus on the ID and discard the tag signal properties like backscatter signal amplitude, operating frequency and phase. In our research, we manipulate these signal properties to encode sensing information. For example, what if crossing a temperature threshold snapped off part of an RFID tag's antenna and caused a massive drop in signal amplitude, or what if a change in moisture content changed the operating frequency of the tag?

The research challenge is achieving a transduction between the parameter of interest and the signal properties of an RFID tag. This is achieved using novel electromagnetic structures and the use of electrically responsive smart materials:

Tag signal amplitude for sensing: An RFID soil moisture sensor

An RFID tag with a monopole probe serves as a cost effective soil moisture sensor
A monopole probe attached to a UHF RFID tag serves as a cost-effective soil moisture sensor. Moisture changes in soil cause changes in the backscatter signal of the RFID tag

Drop in tag signal performance as water is added and then recovery of signal as the soil dries out. In comparison, a reference RFID tag without monopole attachment has a relatively steady signal performance over the period of experimentation

Tag operating frequency for sensing: An RFID fluid level detector

RFID tag designed to be detected across all frequencies in the 902-928 MHz ISM band when the glass is empty

Same RFID tag is only detected in the 920-928 MHz band when the glass is filled with fluid

Some other modalities

Blood anomaly detection

Temperature alarm sensing using shape memory polymers

Crack detection in construction materials

Light intensity sensing using off-the-shelf photoresistors

For more information and questions contact Rahul Bhattacharyya