An Optimized Phase-Controlled Metasurface-Based Low-Profile Folded Transmitarray (FTA) Antenna

In this work, a low-profile wideband folded transmitarray (FTA) antenna has been reported in Ku-band. The proposed FTA has been designed by using phase-controlled 3-bit unit-cells (UCs) based subwavelength metasurface (MS) structure. To achieve the wideband response of the UCs, the generalized scattering matrix (GSM) method is used. Also, a low-profile differential V-shaped microstrip patch antenna (DVMPA) is designed as the FTA feed to achieve low cross-polar levels, and symmetrical pattern throughout the frequency range. Furthermore, the metaheuristic optimization algorithm incorporating particle swarm optimization (PSO) technique is used for the phase distribution of the transmitarray (TA) aperture for realizing wideband flat response with low sidelobe level (SLL) and constant aperture efficiency (AE) throughout the frequency band. The peak gain of the FTA antenna is 22.7 dBi with an AE of 42.5% by maintaining a reduced profile height-to-diameter ratio (H/D) of 0.13. Further, the 1 and 3-dB gain bandwidths (GBWs) are found to be 4.23 and 8.17 GHz, respectively, viz., 28.2% and 54.5% along with suppression of SLLs by over 18 dB throughout the band of operation; thereby offering significant performance improvement compared to its closest competitors. The proposed FTA antenna can be used in Ku-band radio astronomy, space communication, synthetic aperture radar (SAR), and other allied fields requiring high-directive antennas.