Wideband Linearly Polarized Over-2-Bit Transmitarray Antenna for Millimeter-Wave Applications

A wideband linearly polarized over-2-bit transmitarray antenna (TA) using the receiving-transmitting (R-T) scheme in the millimeter-wave band is presented in this work. The TA unit consists of two rectangular patches with a pair of bent branches, and the patches are connected by a metalized via. Two methods are used in this TA to obtain an over-2-bit phase shift of 0–${90}^{\circ }$ and 180–${270}^{\circ }$ from 18 GHz to 30 GHz. Firstly, ${180}^{\circ }$ phase resolution is obtained by rotating the receiving patch around via by ${180}^{\circ }$. Secondly, by tuning the connection position between the branches and rectangular patch of the TA unit cell, a continuous ${90}^{\circ }$ phase shift is further achieved. A TA prototype with $20\times 20$ units is designed, fabricated, and measured. The measured 1 dB and 3 dB gain bandwidth is 24.9% (24.47–31.43 GHz) and 46.96% (20.45–33 GHz) respectively, with a peak gain of 25.17 dBi and a peak aperture efficiency of 55.2%. The measured results agree well with the simulated ones.