By doing so, the designer has the optimum solution, i.e. Two similar FSS array boards were manufactured to check their response as cascaded, with a view towards narrowing the frequency response for the 6-GHz frequency range.įSSs, being periodic arrays, can be developed based on an approach where a single cell is designed, and the boundary conditions emulate an infinite array.
Then the frequency was decided to be scaled down, in order to guarantee a safer margin concerning the fabrication process. This X-band array was constructed by a third-party local company specialized in Printed Circuit Board (PCB) prototyping. By not successful it is implied that the measured results were not correlated to those simulated by CST Microwave Studio®, a 3-D electromagnetic field solver. The 6-GHz frequency range was chosen to test the available prototyping capabilities - a similar previous project on the X-band (10 GHz) was not successful due to a large variation in the geometric dimensions of the array, observed after the fabrication. The chosen design frequency was around 6 GHz, having a band-pass characteristic (so that it can be placed in an aeronautical radome). The RCS within the antenna frequency range will not change, since, ideally, the FSS array will be transparent to it, but those outside the band-pass region can be significantly lowered, due to the fact it will be opaque and reflect the incoming signals with scattering angles different from those of a simple dielectric radome ( Kraus and Marhefka 2002 Singh et al.
One way to reduce the RCS of the vehicle, thereby producing stealth characteristics, is by placing a band-pass FSS radome in front of the antenna, which lets signals within the antenna frequency range go through and blocks out-of-band signals. In the case of stealth vehicles, antennas are one of the main factors that lead to high Radar Cross Section (RCS) figures, due to their inherent resonant characteristics ( Knott et al. Other applications involve dichroic reflectors - where two different frequency signals share the same reflector structure, and the FSS is opaque to one band but transparent to the other ( Munk 2000) - or absorber screens for electromagnetic energy ( Engheta 2002), in applications such as for reducing unintended emissions for electromagnetic compatibility purposes. They have several different applications one of the most famous is in radomes - a cover placed to protect an antenna ( Kraus and Marhefka 2002). Given the quarter-wavelength distance associated to the structure, it has an inherent narrow bandwidth performance, alleviated by some loading techniques and further geometrical variations ( Abdelaziz 2008). They can be seen as an evolution from Salisbury screens, a primitive spatial filter these screens consist of electromagnetic radiation absorbing material layer backed by a metallic plate positioned at a quarter-wavelength distance ( Knott et al.
FSSs can be seen as filters that operate on free-space waves, in contrast to lumped or distributed filters that are based on guided waves or transmission lines. A Frequency Selective Surface (FSS) possesses electromagnetic transmission properties that vary with frequency ( Kraus and Marhefka 2002).