High-Efficiency Wideband Transmitarray Antenna Using Polarization-Rotating Elements with Parasitic Stubs

A high-efficiency polarization-rotating transmit array antenna (T A) using wideband elements is proposed for millimeter-wave applications. The polarization-rotating element consists of three metallic layers and two substrates. Orthogonal polarizers are employed on the top and bottom of the element. And the split ring with a parasitic stub on the middle layer is symmetric about the diagonal, performing the polarization rotation and phase compensation simultaneously. A parasitic stub is designed to decrease transmission loss and broaden the bandwidth. The periodicity of the element is only 1/4 wavelength at 30 GHz. A prototype TA with 28 × 28 elements is designed, fabricated, and measured. The measured peak gain reaches 27.5 dBi at 37.8 GHz. The 1-dB gain drop bandwidth is 30.8-40 GHz (26.0%). The aperture efficiency reaches as high as 71% at 31.5 GHz. Within the bandwidth of 26.5-38.8 GHz (37.7%), the aperture efficiency is higher than 50%. The proposed polarization-rotating TA features wide bandwidth and high efficiency, demonstrating great application potential for 5G millimeter-wave communication.