Bandwidth Improvement Methods of Transmitarray Antennas

Despite several advantages of planar transmitarray antennas compared to conventional lens antennas, they have a narrow bandwidth. The goal of this paper is to improve the bandwidth of transmitarray antennas through the control of the transmission phase range and the optimization of the phase distribution on the transmitarray aperture. To validate the proposed approaches, two quad-layer transmitarrays using double square loop elements have been designed, fabricated, and tested at Ku-band. The transmission phase distribution is optimized for both antennas, while they differ only in the transmission phase ranges. It is shown that the transmitarray antennas designed using the proposed techniques achieve 1-dB gain bandwidth of 9.8% and 11.7%, respectively. The measured gains at 13.5 GHz are 30.22 and 29.95 dB, respectively, leading to aperture efficiencies of 50% and 47%, respectively.