Design of X-band frequency selective surface (FSS) with band pass characteristics based on miniaturized unit cell

Abstract

In this manuscript a multi-layered miniaturized-element frequency selective surfaces (MEFSSs) having band pass characteristics is proposed. The frequency selective surface (FSS) is design at X-band and exhibits harmonics free frequency band upto 30 GHZ, which is suitable for the radar cross section (RCS) reduction of an object. The metallic layers are either in the form of capacitive patches or inductive wires mesh at very small sub-wavelength periods. The multiple closely spaced metallic capacitive layers act as a single capacitive layer with increased capacitance. This technique reduces the unit size cell drastically. As a result the natural resonant frequencies of the structure are shifted to very high frequencies. Thus, the unwanted transmission bands caused by these high order harmonics are shifted to an extremely high band. Using this technique, an MEFSS with a second-order band pass response is designed to operate at 10 GHz. The elements which constitute the FSS are non-resonant structures which are combined to make a second-order band pass filter. The MEFSSs unit cell size, thickness and the inter element spacing are significantly smaller than the wavelength. This overall small size makes the structure a second order band pass spatial filter with excellent stable performance with different angles of incident. The MEFSSs exhibit a stable frequency response to different angles of incidence and polarizations. Moreover, the FSS found numerous applications in communication, microwave, millimeter wave and radar systems such as spatial filters, radar absorbing materials (RAM), artificial magnetic conductors (AMC), planar lenses, radomes, sub-reflectors, polarizer and reflect arrays antennas.