A Novel 2-B Multifunctional Active Frequency Selective Surface for LTE-2.1 GHz

This paper proposes a 2-b multifunctional active frequency selective surface (MAFSS) whose structure is made up of two metallic layers printed on both sides of an F4BME substrate, measuring $320 \times 320 \times 0.8$ mm³. The PIN diodes, embedded on two metallic layers, are controlled through two independent sets of external dc bias network. No additional feeder lines are considered necessary within the MAFSS array, which weakens the bias network's negative impact on the transmission characteristics of the MAFSS. Using an innovative and effective diode switching technique, two functions (electromagnetic switch and polarization selection) and thus four working states (dual-polarized bandpass for code “00,” dual-polarized shielding for code “11,” TE wave selection for code “10,” and TM wave selection for code “01”) have been realized. The equivalent circuit method and the surface current analysis have been used for a better understanding of the physical principles of the design. A prototype of the proposed structure has been fabricated and measured. The measurements have shown a good agreement between the simulated and the measured results, demonstrating thereby that the proposed structure can give excellent performance. Using the results of extensive numerical and experimental studies, the proposed structure has also been proved to give stable performance, with respect to different incident angles and wave polarizations around LTE-2.1 GHz.

I. Introduction

Frequency selective surface (FSS) is a periodic array of suitably arranged metal patches or apertures that functions as a spatial filter [1], [2]. The FSSs, by virtue of their bandpass or bandstop characteristics [3], are widely used in many areas, such as radomes [4], [5], absorbers [6], [7], polarizers [8], [9], radar cross section (RCS) reduction [10], [11], and electromagnetic compatibility [12], [13], in microwave, millimeter-wave, and even terahertz regimes.