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In this work, we propose a new dual-band and dual-circularly polarized spin-decoupled reflectarray (RA) combined with frequency selective surface (FSS)-back that ensure the RA independently operating at Ku / Ka dual-band. First, a double-layer FSS with four concentric square loops is designed to inhibit the mutual coupling between the Ku - and Ka -bands. Second, at each Ku - and Ka -band, the 3 bit coding crossed dipole element is used to realize the spin-decoupling. Moreover, each circularly polarized feed horn generates reflected beam operating with left-hand circular polarization (LHCP)/right-hand circular polarization (RHCP) at Ku - and Ka -bands, respectively. Finally, the RA with a square size of 340 mm is designed, manufactured, and measured to verify its performance. At 12.45 GHz, the measured cross-polarization levels (XPLs) are better than 16.5 and 18.5 dB for LHCP and RHCP radiations, respectively, which show the great spin-decoupling between the two circular polarizations. The measured XPLs are better than 21 and 22.5 dB for LHCP and RHCP at 30 GHz, respectively. The well-performed RA has the perspective in satellite communication systems at both Ku - and Ka -bands.

Mushroom-like electromagnetic band gap (EBG) structures exhibit unique electromagnetic properties that have found a wide range of electromagnetic device applications. This paper focuses on the local resonance behaviors of EBG structures, and a simply locally resonant cavity cell (LRCC) model for mushroom-like EBG structures is presented to gain insight to the physical mechanism of the EBG structures and the interaction of electromagnetic waves with EBG structures. The LRCC model proposes two kinds of main resonance modes: One is the mono-polarized mode that accurately predicts the position of the surface wave suppression bandgap, which is equivalent to the LC parallel resonance based on quasistatic assumption in principle, and the other is the cross-coupling polarized mode that exhibits some interesting resonant phenomena, which has not been observed previously. Parametric studies including the radius effect of the metal plated vias are effectively performed by using the LRCC model. Some numerical simulations and experiments of EBG structures, such as square, triangle, and hexagon lattices, are given to illustrate the applications and validation of LRCC model proposed by this paper.