A Binary Frequency Shift Keying Chipless RFID IoT Switch

This article introduces a Binary Frequency Shift Keying Chipless RFID IoT Switch (BFSK-CIS) as a low-cost and battery-less solution for a relocatable and reprogrammable solution. In this work, the information about the switch's status is encoded as a frequency shift in the frequency spectrum, eliminating the need for reference resonators necessary in the previous amplitude modulation-based approach. The implementation of the BFSK-CIS tag involves using a single-pole-double-throw (SPDT) switch placed between a transmission line and two spiral resonators (each has a unique resonant frequency). Depending on the switch's status, one of the resonators is coupled to the transmission line, thus shifting the resonant frequency of the tag. The BFSK-CIS is passive and designed using commercially available components and a standard PCB fabrication process. Measurement results show the BFSK-CIS tag toggles between two resonant frequencies (i.e.,1.2 and 1.23 GHz) depending on the status of the SPDT switch.