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Multiresonator circuits and RFID chips

Nasir Alfaraj

April 25, 2017 - Posted in Discussion
​​A multiresonating circuit generates a unique spectral signature in response to an interrogation signal sent by an external tag reader (interrogator). A spectral signature is a collection of reflected and attenuated interrogation signals at varying frequencies that collectively define a spectral ID. Spiral resonators are designed to resonate at a particular frequency to create a stopband. When the signal is attenuated at a particular frequency, it signifies a logic “0”; otherwise, it is logic “1”. Furthermore, the stopbands introduce “phase ripples” to the interrogation signal at their resonant frequencies, which can be identified as a phase variation at the interrogator end.

According to [1], radio-frequency identification (RFID) is a process for automatically tracking and identifying objects wirelessly utilizing radio-frequency electromagnetic fields as a means for transferring data. A typical RFID system consists of three major components [1]:

i. Interrogator: sends the interrogation signals to an RFID transponder
ii. Transponder: contains the identification code
iii. Middleware software: maintains the software protocol to process ID data from the interrogator

A chipless RFID tracking system requires an RFID tag (transponder) to receive and retransmit interrogation signals and an RFID reader (interrogator) to communicate with the tag [1]. A block diagram of a typical RFID tracking system is shown in Fig. 1.

Figure 1. Block diagram of a typical RFID tracking system. Adapted from [1].

[1] Preradovic, S., Balbin, I., Karmakar, N., & Swiegers, G. (2009). Multiresonator-based chipless RFID system for low-cost item tracking. IEEE Transactions on Microwave Theory and Techniques, 57(5), 1411–1419.
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