A Multi-port Formulation for Electromagnetic Coupled Auto-tuning RFID Antennas

Arrangements of closely coupled UHF RFID tags are common in the industrial labelling and sensing of vaccines, and of stacks of small objects in general. The mismatch effect of coupling can be mitigated by the new family of auto-tuning ICs having a dynamic internal impedance. A network model is here introduced for the first time with the purpose to predict the response of sets of coupled auto-tuning tags. The analytical model reduces to a closed form description of the tags retuning capability in the particular case of two items in symmetric arrangement. Preliminary experimentations corroborate the theoretical dynamic responses of the ICs w.r.t. variable inter-tag distance. The model can be useful for a better understanding of the potentiality of this class of devices and to optimize their performance for advanced identification and sensing.