  This article presents a bandpass frequency selective surface (FSS) with a
narrowband frequency response. The designed FSS is made of miniaturized
elements unit cell. The operation principle of the FSS is explained by using an
equivalent circuit model, where the passband bandwidth can be controlled by the
values of the circuit elements corresponding to the geometrical dimensions of
the unit cell. The compatibility of the presented structure in designing higher
order narrowband filtering responses is verified by designing a second-order
bandpass FSS with 8:5% fractional bandwidth with a center frequency of 2:7 GHz.
