Dual band, low profile and compact tunable frequency selective surface with wide tuning range

In this paper, a dual polarized, dual band, low profile, embedded bias network, and compact tunable varactor band pass frequency selective surface (FSS) is designed with a wide tuning range. The proposed FSS is composed of two metallic layers printed on both sides of the substrate, where the top side has two cross strips with different dimensions encircled with high pass grids, whereas the bottom side includes a proper bias network. The loaded varactors between the grids and the cross strips with a designed bias network achieve two independent tunable pass bands. Moreover, an equivalent circuit of the FSS is extracted, which show good agreement with the full wave simulation results. The proposed FSS can operate from 2.28 GHz to 4.66 GHz and from 5.44 GHz to 11.3 GHz by proper tuning of the varactors loaded in the large and small cross strips. The tunable range of the low and high pass bands are about 70% with respect to the center frequency of each pass band. The electrical dimensions of the proposed FSS are about $0.05\lambda\times0.05\lambda$, where $\lambda$ is the free space wavelength at a lower pass band (2.28 GHz). Moreover, the proposed FSS works properly up to $60^\circ$ incident angles.