Analytical design of low-profile wideband multi-layer transmitarray antenna for Ku band

A wideband transmitarray antenna with an array of 11 × 11 unit cells is presented in this article. The low profile high gain transmissive surface consists of two substrateless trilayer slotted sheets at 12 GHz. The equivalent circuit model of the proposed unit cells considered as a wideband band-pass filter frequency response. The scattering matrix of the multilayer frequency surface unit cells, extracted from cascaded slotted conductor layers and the air gaps. The optimization technique, particle swarm optimization, is employed to enhance the desired transmitarray antenna, using adjusting the air gaps between layers. Hence, uniform phase distribution is synthesized in the transmission aperture using optimized air gap thicknesses. The length of the suggested unit cells slots varied to satisfy the required 360° phase distributions on the transmission aperture. The required transmission phase range is obtained by two air gaps separated trilayer slotted elements. Using no dielectric layers in desired antenna design, caused the low profile and low transmission loss advantages, lead to near 1 (0-dB) transmission coefficient through the whole range. To validate the design, a model of the transmitarray antenna was fabricated and measured at 12 GHz. The planned antenna has the desired measured results, 26.7 dB peak gain and 1-dB gain bandwidth from 11 to 12.9 GHz equal 15.84%, with 41.7% aperture efficiency at 12 GHz, considering implementation losses such as mismatching, and conductor losses. The symmetric configurations of the developed unit cell can also be used for designing dual-polarized or circularly polarized antennas.