Study of factors influencing performance of substrate backed FSS for millimeter wave atmopsheric remote sensing

A Frequency Selective Surface (FSS) on 175 μm thick quartz with gold trace and unit cell size of 728 μm × 728 μm was proposed in our earlier work for isolating three bands in 50 GHz-200 GHz range for passive atmospheric remote sensing. In this work, we present the factors influencing the performance of substrate backed FSS on frequency de-multiplexing. 3D numerical modeling is used to investigate the influence of the thickness of the gold trace and fabrication tolerance on FSS transmission loss. The design and optimization of the micro fabrication process flow for FSS realization are presented in detail. Scanning electron microscopy (SEM) images confirmed a nearly uniform gold deposition (1.85 μm) across the 35 mm × 35 mm FSS structures with ±2 μm fabrication tolerance on the unit cell dimensions. Continuous wave THz measurements of the fabricated samples showed at least 10 dB and 0.5 dB transmission losses in the reflection and transmission bands respectively for TE polarization and varying angle of incidence (0° to 45°). This study concludes that polarization insensitive millimeter wave FSS with low loss and angle stability is possible on dielectric substrate for atmospheric remote sensing.