Dielectric properties of chiral honeycombs – Modelling and experiment

Abstract

Electromagnetic properties of mechanically chiral honeycomb structures are investigated. In extension to previous works on the subject, rigorous analysis is performed above the quasi-static frequency range. Theoretical considerations and full wave 3D electromagnetic simulations are conducted to prove that, for the honeycombs of interest, higher order harmonics due to structure periodicity are attenuated away from the panel surface at frequencies up to several GHz, which covers a number of popular ISM bands. As a consequence, only individual plane TEM waves are observable at practical locations of transmitters and receivers away from the panel. Under the same conditions, it is demonstrated that the structural chirality does not translate into chiral electromagnetic behaviour. In other words, orthogonal modes of the honeycomb scenarios are linearly polarised, and transformation of the electromagnetic energy into heat occurs purely as a result of classical conductivity or loss tangent, which are low for the low-density panels made of low-loss dielectric cores. This indicates that EMC or shielding characteristics can only be designed either by utilizing the phenomenon of wave reflections, or by equipping the panels with additional foils on surfaces or absorbing foams in air volumes. While precise measurements of final-sized honeycomb panels remain as a challenging task for further work, preliminary experiments have been performed showing good agreement with theoretical and computed predictions.