# Microwave frequency selective surface (FSS)

A Frequency Selective Surface (FSS) is a type of electromagnetic structure that allows certain frequencies to pass through while reflecting or blocking other frequencies. It is composed of a periodic array of conductive or dielectric elements that are spaced apart at a distance that is much smaller than the wavelength of the electromagnetic radiation. The FSS can be designed to selectively filter and manipulate the electromagnetic waves that pass through it based on the geometry, spacing, and material properties of its constituent elements. It is often used as a passive component in microwave and millimeter-wave devices, such as antennas, radars, filters, and absorbers.

This example provides a demonstration of a microwave FSS composed of copper cross structures. Due to its very thin copper layer (0.1 mm) compared to the wavelength (~2.5 cm), we model the copper layer as a 2D surface conductivity to ensure computational efficiency. The FSS has been designed to exhibit a stop band at 12 GHz, where the transmission (S21) reaches as low as -50 dB. By visualizing the field distribution at the resonant frequency, we can observe the dipolar resonance feature of the copper structure. This simulation showcases the effectiveness of FSSs as passive components in microwave devices, and their ability to manipulate electromagnetic waves with high precision.

To view the full example in Python, please click here (opens new window).