Theoretical analysis of backscattering from dielectric sphere for design of THz tags

The electromagnetic backscattering from an isolated spherical dielectric resonator is investigated for its potential application as a chipless and retrodirective tag. The motivation to use a dielectric resonator is its zero conduction loss, thereby being ideally suited to a low-power terahertz operation. The theoretical analysis is done using Mie theory, addressing the natural electromagnetic modes of an isolated spherical scatterer, and interference of the fundamental dipole modes pertaining to directive backward scattering. The working principle, optimized design and practical limitations of the envisaged tag design are discussed taking into consideration engineering trade-off and low-cost system design.