26-04-06 17:03
Age: 2 yrs

BY: COLE, PETER H.

The fundamental principles governing electromagnetic coupling between an interrogator and its labels in an RFID system have been outlined, and a set of concepts suitable for describing cou¬pling in the near and far fields, using electric field, magnetic field or electromagnetic field sensitive antennas, have been defined. Algorithms for the reading of large label populations at UHF and at HF have been described. Some of the properties of electric field and magnetic field antennas have been derived. Some important theorems about optimising antenna sizes and operating frequencies subject to electromagnetic compatibility regulations have been derived. Optimisation policies which can be pursued in the near field, the mid field or the far field have been identified. A proposal for relaxation of electromagnetic compatibility regu¬lations in a narrow band in the HF region is investigated, and some of the interesting consequences for HF operation at substantially improved distances have been identified. These results, while at¬tractive, are unlikely, without substantial increase in label antenna sizes, to challenge the supremacy of far-field systems for long-range RFID system operation.

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