A wideband beam steering transmitarray antenna for Ka-band applications

In this paper, a broadband transmitarray antenna is designed to achieve beamsteering ability with high aperture efficiency for 5G communication systems. To this end, at first an innovative unit cell is designed based on constructive mutual coupling with 1-bit phase quantization (0°/180°), utilizing the current reverse technique. The proposed unit cell includes a modified patch array on top of the upper substrate (Tx) and two modified patch arrays on the bottom of the lower substrate (Rx). A metalized via-hole connects both layers. The results illustrate low insertion loss, consistently preserved across all phase configurations, alongside a broad 3-dB transmission bandwidth spanning from 25.82 GHz to 38.57 GHz (12.75 GHz). This is because the intensity of the current distribution varies across frequencies in the proposed unit cell. By combining these varying amplitudes across frequencies, the design achieves a wider bandwidth (BW). Next, a transmit array antenna is constructed using the proposed unit cell to confirm the beam-forming principle. The results indicate accurate beam steering to the intended angles with decent sidelobe levels, accompanied by an antenna gain increase of 12.22 dBi over its feed, reaching 25.52 dBi at 28 GHz. This significant gain results in an aperture efficiency of 41.6%. Besides, the −3 dB gain ranges from 26.8 to 36.1 GHz (9.3 GHz), corresponding to a bandwidth of 33.3% at the center frequency of 28 GHz. This enhancement stems from incorporating two unit cells in one unit cell, half-elliptical and rectangular-shaped patches, forming an array. To the best of the authors’ knowledge, the proposed transmitarray antenna outperforms existing designs in terms of −3 dB gain bandwidth and aperture efficiency, representing a substantial contribution to the field of 5G antenna technologies.