Modified Dielectric Frequency Selective Surfaces With Enlarged Bandwidth and Angular Stability

The analysis of a dielectric stop band filter is performed in terms of modified dielectric frequency selective surfaces (MDFSS). In fact, an MDFSS can totally reflect the power if a plane wave impinging on it excites a leaky wave, acting thereby as a stop band filter. Its relative bandwidth is about 0.5-0.7% and it can be enlarged by cascading MDFSSs. The development of such a cascade is analyzed in order to obtain a larger relative bandwidth. Unfortunately, the frequency behavior of the cascade is influenced by θ, the angle of incidence of the impinging plane wave. In fact, if the stop band filter is developed at f₀ for normal incidence, not only does it not maintain the same bandwidth for θ ≠ 0^° but it also moves its central frequency toward other values with lower bandwidth and loses its stop band characteristic in a range of a few angles. This effect, known as angular stability, can be mitigated by cascading MDFSSs resonating at different angles of incidence. In this case, the choice of the MDFSSs plays an important role and it will be shown that the relative bandwidth can be maintained in the angular range 0-30°.