On the Detection of Frequency-Spectra-Based Chipless RFID Using UWB Impulsed Interrogation

A novel approach is presented to accurately estimate the resonant features of a multipatch backscatter-based chipless radio frequency identification (RFID) tag. An ultra-wideband impulse radar (UWB-IR)-based reader interrogates the chipless tag with a UWB pulse, and the received backscatter is analyzed in the time domain. The key components constituting the backscattered signal, the structural mode, and the antenna mode are identified, and their spectral content are analyzed. Analysis shows that the antenna mode backscatter contains the information carrying signal while the structural mode backscatter contains no information about the tag. A semi-analytical model is developed to explain the behavior of the signal backscattered from the chipless RFID tag. Simulation and semi-analytical results are validated by experimental measurements obtained in an anechoic chamber environment using a 4-b multipatch chipless RFID tag. The new method does not rely on calibration tags for operation and has a greater degree of freedom in the orientation of tags with respect to a reader. A novel method, selective spectral interrogation (SSI), that uses a set of interrogation pulses to extract information bits stored in the spectral signature of the chipless tag is also introduced.