Ultrathin High-Gain D-Band Transmitarray Based on a Spatial Filter Topology Utilizing Bonding Layer Effect

Abstract

This letter presents an ultrathin transmitarray (TA) in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> -band (110–170 GHz) by utilizing the bonding layer effect of spatial filters. The standard printed circuit board process limits the performance of spatial filters, resulting in a poor phase-shifting range in the sub-terahertz. The proposed unit cells based on the frequency selective surfaces use only two substrates to be ultrathin. By attaching the additional metal layer on the other side of the bonding substrate, the bonding layer effect can be maximized. Consequently, the proposed unit cells achieved a 271° phase-shifting range without any additional substrates. The proposed TA is the first to attain a high gain of more than 40 dBi in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> -band by reducing the quantization loss. The TA is synthesized using ten types of unit cells that have a low insertion loss of less than 1.5 dB. A 25.5 dBi horn antenna was selected as the source. The focal-to-diameter ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</i> / <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> ) ratio is 1.686 for the TA. The proposed TA, which is comprised of 50 176 elements, attains a peak gain of 44.3 dBi, an efficiency of 24.1%, and a bandwidth of 6% (134.5–143.5 GHz).