Optically Transparent Tri-Wideband Mosaic Frequency Selective Surface with Low Cross-Polarisation.

Nur Biha Mohamed Nafis,Raimi Dewan,Mohamad Kamal A Rahim,Mohamed Himdi,Osman Ayop

doi:10.3390/ma15020622

Abstract

Acquiring an optically transparent feature on the wideband frequency selective surface (FSS), particularly for smart city applications (building window and transportation services) and vehicle windows, is a challenging task. Hence, this study assessed the performance of optically transparent mosaic frequency selective surfaces (MFSS) with a conductive metallic element unit cell that integrated Koch fractal and double hexagonal loop fabricated on a polycarbonate substrate. The opaque and transparent features of the MFSS were studied. While the study on opaque MFSS revealed the advantage of having wideband responses, the study on transparent MFSS was performed to determine the optical transparency application with wideband feature. To comprehend the MFSS design, the evolutionary influence of the unit cell on the performance of MFSS was investigated and discussed thoroughly in this paper. Both the opaque and transparent MFSS yielded wideband bandstop and bandpass responses with low cross-polarisation (−37 dB), whereas the angular stability was limited to only 25°. The transparent MFSS displayed high-level transparency exceeding 70%. Both the simulated and measured performance comparison exhibited good correlation for both opaque and transparent MFSS. The proposed transparent MFSS with wideband frequency response and low cross-polarisation features signified a promising filtering potential in multiple applications.

Highlights

Future interest in the rapid evolution of 5G technology and the development of smart cities requires antennas [1,2,3] and frequency selective surfaces (FSS) to be optically transparent when integrated into the existing infrastructures [4]
This is because the trace width of the metallic conductor of the previously proposed FSS structural element exceeded 0.8 mm, in which the metallic conductor occupied a wide area of the FSS unit cell and decreased the optical transparency of the FSS
In comparison with transparent mosaic frequency selective surfaces (MFSS) proposed in past studies, the transparent MFSS proposed in this present study displayed the advantage of having wideband bandstop and bandpass responses, as well as the ability to provide high optical transparency above 70.3%, but angular stability limited to only 25◦

Summary

Introduction

Future interest in the rapid evolution of 5G technology and the development of smart cities requires antennas [1,2,3] and frequency selective surfaces (FSS) to be optically transparent when integrated into the existing infrastructures [4]. This study proposes a high optically transparent single layer mosaic frequency selective surface (MFSS) with wideband bandstop and bandpass frequency responses, as well as low cross-polarisation. When the unit cell evolved to FSS 3, the simulated Txx frequency response exhibited bandstop responses at low- and high-frequency bands with a bandpass frequency response, which is generally portrayed by the combination of the patch and slot geometry [6]. The frequency responses of the proposed MFSS for both TE and TM spacing between adjacent unit cells or the periodicity of the unit cell is electrically large, which eventually deteriorates the performance of the FSS when the EM wave hits the sur‐. The magnetic field of the opposite direction generated by the horizontal surface current distribution cancelled each other, led to low cross-polarisation and high isolation from the co-polarisation value

Optical Transparency of MFSS

Experiment

Comparative Study

Findings

Conclusions