Frequency selective surfaces on building materials - air gap impact

It is demonstrated how frequency selective surfaces (FSSs) can be deployed on conventional building materials, so as the FSS frequency response is not affected by the building material. This effectively means that the two surfaces, the FSS and the building wall surface, will affect radio propagation independently based on their own characteristics. When FSSs are attached to building walls, they can suffer significant detuning, compared to free-standing frequency response, which appears to fade away as the air gap between the two surfaces increases. Simulations and anechoic chamber measurements demonstrate that a ´break-point´ air gap exists, beyond which the FSS response is not affected by the presence of the building wall.