Design of Polarizing Cells for Broadband Reflectors

This paper presents the topology of two cells that can be used to conceive periodic polarizing reflectors. These reflectors are capable to convert a linearly polarized incident wave to a circularly polarized reflected one. Two polarizer designs are presented and their performance is validated through simulated results. I. INTRODUCTION Polarizers are fundamental elements in several communications and remote sensing applications [1]. Polarizing surfaces convert a linearly polarized (LP) wave into a circularly polarized one, thus allowing to replace CP radiators by simpler LP ones [2]. These surfaces can operate either in reflection [3] or in transmission [4], and they are usually made of metallic scatterers which are periodically arranged and printed on single or multiple layers of dielectric substrates [5], [6]. In this contribution, we are interested in conceiving periodic reflecting surfaces operating over a wide frequency range. Multiple works have been already reported in the literature aiming at this purpose. All proposals consider an LP source slanted by 45 • illuminating the structure, and three main design strategies can be identified. The first one is to use a scatterer including two perpendicular resonators [1], [7]. Both these resonators are excited by the impinging LP wave. The key point of this solution is the fact that the associated resonance frequencies are slightly shifted in frequency, thereby generating the desired 90 • phase difference between the two components, and therefore, a CP reflected field. Since this approach is based on a resonance phenomena, it normally operates only over a reduced bandwidth. The second strategy uses non-resonant patterns which behave as a capacitor or an inductor depending on the considered component of the incident electric field [3], [5]. Classical patterns presenting this behavior are meander lines. By properly tuning the values of such reactive components, 90 • phase shift can be obtained between the orthogonal components of the reflected field. By cascading various of these gratings, broadband CP conversion can be attained. The third strategy considers multilayer structures where each layer is in charge of interacting mainly with only one of the orthogonal components of the incident field [4], [6]. Wideband behavior can be again attained, since the considered scatterers are normally non resonant. However, multilayer dielectric structures are normally avoided in space applications. Our objective is therefore to attain broadband CP conversion employing only one PCB layer. In this paper, two new designs of polarizing cells are presented, which are fundamentally based on the secon