RFID Grids: Part I—Electromagnetic Theory

Abstract

The close displacement of UHF RFID tags can be considered as an electromagnetic interconnected system having specific properties. The so denoted RFID Grid includes single-chip tags in close mutual proximity or a single tag with a multiplicity of embedded microchips. A multi-port scattering framework is used to derive the macroscopic parameters governing the system response which could be optimized for the specific application. Moreover, unique features are introduced, such as the possibility to improve the power scavenging and the generation of analog identifiers and fingerprint. The last ones are electromagnetic responses independent on the position and orientation of the reader and on the nearby environment, with great relevance for Sensing and Security.

Passive UHF RFID antennas for sensing applications: Principles, methods, and classifcations

“…Before going into a particular sensing problem, it is hence useful to introduce the basic RFID e.m. parameters suitable to sensing purposes. A single-chip configuration is considered throughout the paper, but the same ideas may be nonetheless extended to the multi-chip systems recently introduced in [10], [11], [12].…”

“…Finally, forward (1) and backward (2) powers may be combined at turn-on condition with the purpose to drop out the influence of the distance and of the reader's and tag's gains and orientation [11], [12]. A non-dimensional indicator ( Fig.3c), denoted as Analog Identifier (AID), can be hence introduced:…”

“…The RFID GRID theory in [11], [12] provides all the required equations and procedures to manage multi-chip antennas which is a problem similar to the design of multi-ports loaded scatterers.…”

Optimization of multichip RFID tag antenna with genetic algorithm and method of moments

“…In [3], the concept "grid" is introduced, which represents a generally coupled multitude of UHF tags, including standalone tags in close mutual proximity as well as tags with a multiplicity of embedded RFID microchip transponders able to achieve advanced capabilities such as redundancy and sensing; also it's fully investigated as an EM interconnected system. In our work, we take the latter formation of grid, i.e., a tag with multiple chips connected to it; this tag can be handled as a multi-port antenna.…”

“…The passive part (metallization) of the multi-chip tag is automatically designed to optimize the global parameters introduced and discussed in [3], rather than individual radiation or (multi-port) impedance matching, which is a novel approach. The global parameter is named embedded realized gain and it closely integrates parameters like impedance matching, gain and polarization factor into a single parameter.…”