Summary
International Symposium on Antennas and Propagation
2010
Session Number:4FB3
Session:
Number:4FB3-5
FSS Sandwiched Reflectarray for Dual?frequency Application
Jianfeng Li, Qiang Chen, Qiaowei Yuan, Kunio Sawaya,
pp.-
Publication Date:2010/11/23
Online ISSN:2188-5079
Summary:
Microstrip reflectarray has attracted significant interest because of its planar structure, surface mountable and low cost. It has been constantly developed for many years and the most recent researches have been focused on dual-band/polarization, beam scanning and so on [2-5]. However, the reflection phase range is the main limitation of reflectarray, especially for dualfrequency system. For a single-layer substrate, the achievable phase range of a traditional reflectarray is approximated to 360? x (1.0 - kh/π ) , where k is a wavenumber in the substrate and h is the substrate thickness [6]. It can be seen that a thinner substrate offers a wider reflection phase range at the cost of high nonlinear. A rapid variation around the patch resonance makes the design difficult due to manufacturing errors. On the other hand, a thicker substrate offers a much smoother phase variation. However, the phase range becomes narrow, which makes practical designs unfeasible. Thus, for a dual-frequency system, a substrate may be too thin to have smooth phase range at lower frequency resulting slope; at the same time, it may be too thick at higher frequency to obtain an enough phase range. Usually, we need a tradeoff between the wide phase range and the smooth linear level. In this paper, a novel concept is proposed to solve this problem. To simultaneously obtain a smooth reflection phase curve, a larger reflection phase range and dual operating frequency bands, an FSS (Frequency Selective Surface) layer is introduced and sandwiched between the reflectarray element layer (RA layer) and the metal ground plane. The FSS layer can act as an additional reflecting plane for the upper frequency. For lower frequency, the FSS layer is transparent so that the metal ground plane acts as the reflection plane. As a result, a smooth and wide reflection phase range can be achieved at both frequencies. Firstly, a new modified narrow band stop FSS is designed to provide a proper additional reflection plane. Moreover, a dual-band and dualpolarization reflectarray comprised cross-dipole elements and sandwiched FSS layer is designed, fabricated and measured to demonstrate the performance. For normal incidence, a maximum directivity of 18.1 dB (58°scattering angle) and 21.2 dB (29°scattering angle) are obtained at 12GHz and 16GHz, respectively.