EPSRC DTP PhD studentship: Ferrite-loaded planar cavity resonators for innovative solutions to the inductive tagging problem

University of Exeter - College of Engineering, Mathematics and Physical Sciences

Main supervisor: Prof R. J. Hicken (University of Exeter)
Co-supervisor: Prof A. P. Hibbins (University of Exeter)

Inductive tagging is an important form of electronic article surveillance (EAS) within the retail sector. The tag is an LC resonator that couples to the 8.2 MHz AC magnetic field generated by a gate antenna. A planar tag has lateral dimensions about 1000 times smaller than the free space wavelength of the AC field, and constitutes a meta-atom that could be replicated to form a metamaterial. Exeter has patented a multiply-folded ferrite-loaded planar cavity resonator tag [1,2], which may be activated while resting on a metallic surface, thereby solving a longstanding problem in EAS. The scientific aims are to vary the cavity geometry and ferrite composition to test models of the cavity resonance, and build arrays of interacting resonators so that their collective modes can be explored. Impact-related aims are to evolve the resonator design for use at RF (13.5 MHz) and UHF (900 MHz) frequencies, to introduce elements that result in deactivation when subject to large pulsed fields, and to assess cross-talk and evaluate the potential of large area metamaterials for antenna and shielding applications. The project will benefit from existing links with Unilever and Llexan International, while a market survey commissioned in August 2016 has indicated strong interest from other EAS companies.

[1] UK patent application No. 1309920.5 for a “Radio Frequency Detectable Device”

[2] “Ferrite-filled λ/4-cavities for compact planar resonators

P. S. Keatley, C. J. Durrant, S. J. Berry, E. Sirotkin, A. P. Hibbins, and R. J. Hicken Appl. Phys. Lett. 104, 022405 (2014). 

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