Polarization- Insensitive, Highly-Selective Metasurface-Based Filtenna for Satcom Applications

This paper presents a planar, polarization-insensitive, space-compatible, skirt-selective filtering transmitarray for satellite communications. The transmitarray employs a double-layer frequency selective surface (FSS) to enable filtering with a sharp roll-off factor. A novel hybrid square ring-modified split ring resonator (SRR) unit cell is introduced by arranging four SRRs in sequential rotation in a rectangular array. The SRRs are integrated with an internal strip and are inductively coupled to each other. Their design is optimized using both numerical techniques and a semi-analytical procedure based on equivalent circuit theory. The sequential rotation of the SRRs enables a stable wide-band response while maintaining a constant impedance to electromagnetic waves impinging on the FSS with either vertical or horizontal linear polarization. The selected unit cell shape allows for achieving a highly selective pass-band response with a significant rejection level and the synthesis of a narrow beam in an array configuration. A single FSS is capable of producing an effective filtering response on its own. This concept lends itself to a higher-order filtering configuration using a double-layer FSS. The double-layer FSS is designed to operate in Ku-Band (with a wideband 10 dB impedance bandwidth of 14.74 % (center frequency <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(f_{O})= 14.8$</tex> GHz), 3 dB transmission bandwidth of 19.1 % <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(f_{O}=14.9$</tex> GHz), and flat 0.2 dB transmission bandwidth of 11.7 % <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(f_{O} =14.74\text{Ghz}))$</tex>, while displaying polarization insensitivity. The achieved roll-off is sharp and is larger than 29 dB/O.25 GHz across both the upper and lower passband edges. Furthermore, the antenna radiates a narrow broadside beam with half power beamwidth lower than 7° and side lobe levels smaller than 12 dB at passband frequencies. Full-wave simulation results are presented and discussed.