A Wideband Multibeam Transmitarray Antenna Based on 3‐D FSS

This paper presents a novel method for designing a wideband dual‐polarised multibeam transmitarray antenna. First, a dual‐polarised element is implemented through a polarisation‐separating, orthogonal‐interleaved three‐dimensional frequency‐selective surface (3‐D FSS). Subsequently, a wideband dual‐polarised unit cell is developed by integrating true‐time‐delay (TTD) technology, allowing full 360° linear phase shifting for distinct polarisations. A superposition method is then employed to efficiently and stably determine the phase distribution of the array, facilitating multibeam radiation. Finally, measurements of the fabricated transmitarray antenna validate its excellent quad‐beam radiation performance at 5 GHz for both vertical and horizontal polarisation, with each beam exhibiting precise spatial separation and maintaining sidelobe levels below −12 dB and cross‐polarisation suppression ratios better than −20 dB. The 3 dB gain bandwidths are measured to be 16.31% for vertical polarisation and 16.96% for horizontal polarisation, with corresponding peak aperture efficiencies of 37.27% and 35.63%, respectively.