FREQUENCY SELECTIVE SURFACES: DESIGN OF BROADBAND ELEMENTS AND NEW FREQUENCY STABILIZATION TECHNIQUES

摘要

Two important features of a frequency selective surface (FSS) are bandwidth and frequency stability. Methods of increasing FSS bandwidth include, among others, decreasing inter-element spacing and increasing the thickness of the supporting dielectric layer. The shape of the FSS element also determines its bandwidth. To achieve any desired bandwidth, a combination of these methods is often required. The present work focuses on designing an FSS element where shape alone is the most important feature in determining its bandwidth. The elements are a combination of two known FSS elements with close resonant frequencies but not located in the same frequency band. The FSS's are designed to act as reflectors. The second part of this paper discusses frequency stabilization techniques, focusing on rectangular arrays of tripoles and cross dipoles. These elements have poor frequency stability with angle of incidence for parallel polarization. Dielectric loading and skewed arrays help minimize the problem. In the present work, a new method based on varying the element's impedance by partially removing the conducting patch at the center of the element is introduced.